botany
   HOME

TheInfoList



OR:

Botany, also called , plant biology or phytology, is the
science Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earli ...
of
plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
life and a branch of
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of Cell (biology), cells that proce ...
. A botanist, plant scientist or phytologist is a
scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...
who specialises in this field. The term "botany" comes from the
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek Dark ...
word (''botanē'') meaning "
pasture Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or Domest ...
", "
herb In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables and other plants consumed for macronutrients, with savory or aromatic properties that are used for flavoring and garnishing food, for medicina ...
s" "
grass Poaceae () or Gramineae () is a large and nearly ubiquitous Family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species culti ...
", or "
fodder Fodder (), also called provender (), is any agriculture, agricultural foodstuff used specifically to feed domesticated livestock, such as cattle, domestic rabbit, rabbits, sheep, horses, chickens and pigs. "Fodder" refers particularly to food g ...
"; is in turn derived from (), "to feed" or "to graze". Traditionally, botany has also included the study of
fungi A fungus (plural, : fungi or funguses) is any member of the group of Eukaryote, eukaryotic organisms that includes microorganisms such as yeasts and Mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified ...
and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
by
mycologists Mycology is the branch of biology concerned with the study of fungus, fungi, including their genetics, genetic and biochemistry, biochemical properties, their Taxonomy (biology), taxonomy and ethnomycology, their use to humans, including as a so ...
and
phycologists Phycology () is the scientific study of algae. Also known as algology, phycology is a branch of List of life sciences, life science. Algae are important as primary production, primary producers in aquatic ecosystems. Most algae are eukaryote, ...
respectively, with the study of these three groups of organisms remaining within the sphere of interest of the
International Botanical Congress International Botanical Congress (IBC) is an international meeting of Botany, botanists in all scientific fields, authorized by the International Association of Botanical and Mycological Societies (IABMS) and held every six years, with the locatio ...
. Nowadays, botanists (in the strict sense) study approximately 410,000
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
of
land plants The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...
of which some 391,000 species are
vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of embryophyte, land plants ( accepted known species) that have lignin, lignified tissue (biology), tissues (the xylem) for conducting water and ...
s (including approximately 369,000 species of
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
s), and approximately 20,000 are
bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and moss Mosses are small, non-vascular flower A flower, sometimes known as a bloo ...
s. Botany originated in prehistory as
herbalism Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remedies ...
with the efforts of early humans to identify – and later cultivate – edible, medicinal and poisonous plants, making it one of the oldest branches of science. Medieval
physic garden A physic garden is a type of herb garden with medicinal plants. Botanical gardens developed from them. History Modern botanical gardens were preceded by medieval physic gardens, often monastic gardens, that existed by 800 at least. Gardens of ...
s, often attached to
monasteries A monastery is a building or complex of buildings comprising the domestic quarters and workplaces of Monasticism, monastics, monks or nuns, whether living in Cenobitic monasticism, communities or alone (hermits). A monastery generally includes ...
, contained plants of medical importance. They were forerunners of the first
botanical garden A botanical garden or botanic gardenThe terms ''botanic'' and ''botanical'' and ''garden'' or ''gardens'' are used more-or-less interchangeably, although the word ''botanic'' is generally reserved for the earlier, more traditional gardens, an ...
s attached to
universities A university () is an educational institution, institution of higher education, higher (or Tertiary education, tertiary) education and research which awards academic degrees in several Discipline (academia), academic disciplines. Universities ty ...
, founded from the 1540s onwards. One of the earliest was the Padua botanical garden. These gardens facilitated the academic study of plants. Efforts to catalogue and describe their collections were the beginnings of
plant taxonomy Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy (biology), taxonomy (the science that finds, describes, classifies, and names living things). Plant taxono ...
, and led in 1753 to the binomial system of nomenclature of
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
that remains in use to this day for the naming of all biological species. In the 19th and 20th centuries, new techniques were developed for the study of plants, including methods of
optical microscopy Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of optical instruments, instruments that use or Photodetector, detect it. Optics usually describes t ...
and live cell imaging,
electron microscopy An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
, analysis of
chromosome number Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mat ...
, plant chemistry and the structure and function of
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
s and other
protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metabo ...
s. In the last two decades of the 20th century, botanists exploited the techniques of molecular genetic analysis, including
genomics Genomics is an interdisciplinary field of biology focusing on the structure, function, evolution, mapping, and editing of genomes. A genome is an organism's complete set of DNA, including all of its genes as well as its hierarchical, three-dime ...
and
proteomics Proteomics is the large-scale study of proteins. Proteins are vital parts of living organisms, with many functions such as the formation of structural fibers of muscle tissue, enzymatic digestion of food, or synthesis and replication of DNA. In ...
and DNA sequences to classify plants more accurately. Modern botany is a broad, multidisciplinary subject with contributions and insights from most other areas of science and technology. Research topics include the study of plant
structure A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...
, growth and differentiation,
reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. Reproduction is a fundamental feature of all known life; each individual org ...
,
biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology a ...
and primary metabolism, chemical products, development,
diseases A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medica ...
, evolutionary relationships,
systematics Biological systematics is the study of the diversification of living forms, both past and present, and the Correlation and dependence, relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: c ...
, and
plant taxonomy Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy (biology), taxonomy (the science that finds, describes, classifies, and names living things). Plant taxono ...
. Dominant themes in 21st century plant science are
molecular genetics Molecular genetics is a sub-field of biology that addresses how differences in the structures or expression of DNA molecules manifests as variation among organisms. Molecular genetics often applies an "investigative approach" to determine the ...
and
epigenetics In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Ancient Greek, Greek prefix ''wikt:epi-, epi-'' ( "over, outside of, around") in ''epigenetics'' imp ...
, which study the mechanisms and control of gene expression during differentiation of
plant cell Plant cells are the cells present in Viridiplantae, green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids ...
s and tissues. Botanical research has diverse applications in providing staple foods, materials such as
timber Lumber is wood that has been processed into dimensional lumber, including Beam (structure), beams and plank (wood), planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as fini ...
,
oil An oil is any nonpolar In chemistry, polarity is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. Polar molecules m ...
, rubber,
fibre Fiber or fibre (from la, fibra, links=no) is a #Natural fibers, natural or Fiber#Artificial fibers, artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The stronge ...
and drugs, in modern
horticulture Horticulture is the branch of agriculture that deals with the art, science, technology, and business of plant cultivation. It includes the cultivation of fruits, vegetables, nuts, seeds, herbs, sprouts, mushrooms, algae, flowers, seaweeds and no ...
,
agriculture Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilization, whereby farming of Domestication, domesticated species created food ...
and
forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forests, woodlands, and associated resources for human and environmental benefits. Forestry is practiced in plantations and natural Stand level ...
,
plant propagation Plant propagation is the process by which new plants grow from a variety of sources: seeds, Cutting (plant), cuttings, and other plant parts. Plant propagation can also refer to the man-made or natural dispersal of seeds. Propagation typically oc ...
,
breeding Breeding is sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes ...
and
genetic modification Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of Genetic engineering techniques, technologies used to change the gene ...
, in the synthesis of chemicals and raw materials for construction and energy production, in
environmental management Environmental resource management is the management Management (or managing) is the administration of an organization, whether it is a business, a nonprofit organization, or a government body. It is the art and science of managing resou ...
, and the maintenance of
biodiversity Biodiversity or biological diversity is the variety and variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem d ...
.


History


Early botany

Botany originated as
herbalism Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remedies ...
, the study and use of plants for their medicinal properties. The early recorded history of botany includes many ancient writings and plant classifications. Examples of early botanical works have been found in ancient texts from India dating back to before 1100 BCE,
Ancient Egypt Ancient Egypt was a civilization in Northeast Africa situated in the Nile Valley. Ancient Egyptian civilization followed prehistoric Egypt and coalesced around 3100Anno Domini, BC (according to conventional Egyptian chronology) with the ...
,Manniche, Lisa; An Ancient Egyptian Herbal; American University in Cairo Press; Cairo; 2006; in archaic
Avestan Avestan (), or historically Zend, or by the speakers as Upastavakaena ( pas.taˈvakˈaeːna is an umbrella term for two Old Iranian languages: Old Avestan (spoken in the 2nd millennium BCE) and Younger Avestan (spoken in the 1st millennium B ...
writings, and in works from China purportedly from before 221 BCE. Modern botany traces its roots back to
Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean Sea, Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, classical antiquity ( AD 600), th ...
specifically to
Theophrastus Theophrastus (; grc-gre, Θεόφραστος ; c. 371c. 287 BC), a Greek philosopher and the successor to Aristotle in the Peripatetic school. He was a native of Eresos in Lesbos Island, Lesbos.Gavin Hardy and Laurence Totelin, ''Ancient Bota ...
(–287 BCE), a student of
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical Greece, Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatet ...
who invented and described many of its principles and is widely regarded in the
scientific community The scientific community is a diverse network of interacting scientists. It includes many "working group, sub-communities" working on particular scientific fields, and within particular institutions; interdisciplinary and cross-institutional acti ...
as the "Father of Botany". His major works, '' Enquiry into Plants'' and ''On the Causes of Plants'', constitute the most important contributions to botanical science until the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the late 5th to the late 15th centuries, similar to the Post-classical, post-classical period of World history (field), global history. It began with t ...
, almost seventeen centuries later. Another work from Ancient Greece that made an early impact on botany is ''
De materia medica (Latin name for the Greek language, Greek work , , both meaning "On Materia medica, Medical Material") is a pharmacopoeia of medicinal plants and the Medication, medicines that can be obtained from them. The five-volume work was written betw ...
'', a five-volume encyclopedia about
herbal medicine Herbal medicine (also herbalism) is the study of pharmacognosy and the use of medicinal plants, which are a basis of traditional medicine. With worldwide research into pharmacology, some herbal medicines have been translated into modern remedies ...
written in the middle of the first century by Greek physician and pharmacologist
Pedanius Dioscorides Pedanius Dioscorides ( grc-gre, Πεδάνιος Διοσκουρίδης, ; 40–90 AD), “the father of pharmacognosy”, was a Greek physician, pharmacologist, botanist, and author of '' De materia medica'' (, On Medical Material) —a 5-vo ...
. ''De materia medica'' was widely read for more than 1,500 years. Important contributions from the medieval Muslim world include
Ibn Wahshiyya ( ar, ابن وحشية), died , was a Nabataeans of Iraq, Nabataean (Aramaic language, Aramaic-speaking, rural Iraqi) agriculturalist, toxicologist, and alchemist born in Qussīn, near Kufa in Iraq. He is the author of the ''Nabataean Agricultu ...
's ''
Nabatean Agriculture ''The Nabataean Agriculture'' (), also written ''The Nabatean Agriculture'', is a 10th-century text on agronomy by Ibn Wahshiyya (died ), from Qussīn in present-day Iraq. It contains information on plants and agriculture, as well as on Magic (s ...
'', Abū Ḥanīfa Dīnawarī's (828–896) the ''Book of Plants'', and
Ibn Bassal Ibn Bassal ( ar, ابن بصال) was an 11th-century Al-Andalus, Andalusian Arab botanist and agronomist in Toledo, Spain, Toledo and Seville, Spain who wrote about horticulture and arboriculture. He is best known for his book on agronomy, the ' ...
's ''The Classification of Soils''. In the early 13th century,
Abu al-Abbas al-Nabati Ahmad bin Muhammad bin Mufarraj bin Ani al-Khalil, better known as Abu al-Abbas al-Nabati, Ibn al-Rumiya or al-Ashshab, ( ar, أبو العباس النباتي, ''Abu’l-ʿAbbās al-Nabātī'')  (c. 1200) was an Andalusian people, Andalusia ...
, and
Ibn al-Baitar Diyāʾ al-Dīn Abū Muḥammad ʿAbd Allāh ibn Aḥmad al-Mālaqī, commonly known as Ibn al-Bayṭār () (1197–1248 AD) was an Andalusian Arab The Arabs (singular: Arab; singular ar, عَرَبِيٌّ, DIN 31635: , , plural ar, ...
(d. 1248) wrote on botany in a systematic and scientific manner. In the mid-16th century,
botanical garden A botanical garden or botanic gardenThe terms ''botanic'' and ''botanical'' and ''garden'' or ''gardens'' are used more-or-less interchangeably, although the word ''botanic'' is generally reserved for the earlier, more traditional gardens, an ...
s were founded in a number of Italian universities. The Padua botanical garden in 1545 is usually considered to be the first which is still in its original location. These gardens continued the practical value of earlier "physic gardens", often associated with monasteries, in which plants were cultivated for medical use. They supported the growth of botany as an academic subject. Lectures were given about the plants grown in the gardens and their medical uses demonstrated. Botanical gardens came much later to northern Europe; the first in England was the University of Oxford Botanic Garden in 1621. Throughout this period, botany remained firmly subordinate to medicine. German physician
Leonhart Fuchs Leonhart Fuchs (; 17 January 1501 – 10 May 1566), sometimes spelled Leonhard Fuchs and cited in Latin as ''Leonhartus Fuchsius'', was a German physician and botanist. His chief notability is as the author of a large book about plants and th ...
(1501–1566) was one of "the three German fathers of botany", along with theologian
Otto Brunfels Otto Brunfels (also known as Brunsfels or Braunfels) (believed to be born in 1488 – 23 November 1534) was a German theologian and botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of bi ...
(1489–1534) and physician Hieronymus Bock (1498–1554) (also called Hieronymus Tragus). Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification. Physician Valerius Cordus (1515–1544) authored a botanically and pharmacologically important herbal ''Historia Plantarum'' in 1544 and a
pharmacopoeia A pharmacopoeia, pharmacopeia, or pharmacopoea (from the obsolete typography ''pharmacopœia'', meaning "drug-making"), in its modern technical sense, is a book containing directions for the identification of compound medicines, and published by ...
of lasting importance, the ''Dispensatorium'' in 1546. Naturalist Conrad von Gesner (1516–1565) and herbalist
John Gerard John Gerard (also John Gerarde, c. 1545–1612) was an English herbalist with a large garden in Holborn, now part of London. His 1,484-page illustrated ''Herball, or Generall Historie of Plantes'', first published in 1597, became a popular gar ...
(1545–) published herbals covering the medicinal uses of plants. Naturalist
Ulisse Aldrovandi Ulisse Aldrovandi (11 September 1522 – 4 May 1605) was an Italian naturalist, the moving force behind Bologna's botanical garden, one of the first in Europe Europe is a large peninsula conventionally considered a continent in its own ...
(1522–1605) was considered the ''father of natural history'', which included the study of plants. In 1665, using an early microscope,
Polymath A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ...
Robert Hooke Robert Hooke Fellow of the Royal Society, FRS (; 18 July 16353 March 1703) was an English polymath active as a scientist, natural philosopher and architect, who is credited to be one of two scientists to discover microorganisms in 1665 using ...
discovered cells, a term he coined, in
cork Cork or CORK may refer to: Materials * Cork (material) Cork is an Permeability (earth sciences), impermeable buoyancy, buoyant material, the Cork cambium, phellem layer of bark (botany), bark tissue that is harvested for commercial use prima ...
, and a short time later in living plant tissue.


Early modern botany

During the 18th century, systems of
plant identification In biology, determination is the process of matching a specimen of an organism to a known taxon In biology, a taxon (back-formation from ''Taxonomy (biology), taxonomy''; plural taxa) is a group of one or more populations of an organism or or ...
were developed comparable to
dichotomous keys In phylogenetics, a single-access key (also called dichotomous key, sequential key, analytical key, or pathway key) is an identification key where the sequence and structure of identification steps is fixed by the author of the key. At each point i ...
, where unidentified plants are placed into
taxon In biology, a taxon (back-formation from ''Taxonomy (biology), taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known ...
omic groups (e.g. family, genus and species) by making a series of choices between pairs of characters. The choice and sequence of the characters may be artificial in keys designed purely for identification ( diagnostic keys) or more closely related to the natural or phyletic order of the
taxa In biology, a taxon (back-formation from ''Taxonomy (biology), taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known ...
in synoptic keys. By the 18th century, new plants for study were arriving in Europe in increasing numbers from newly discovered countries and the European colonies worldwide. In 1753,
Carl von Linné Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his ennoblement Ennoblement is the conferring of nobility—the induction of an individual into the noble social class, class. Currently only a few kingdoms still grant no ...
(Carl Linnaeus) published his
Species Plantarum ' (Latin for "The Species of Plants") is a book by Carl Linnaeus, originally published in 1753, which lists every species of plant known at the time, classified into genus, genera. It is the first work to consistently apply binomial nomenclature ...
, a hierarchical classification of plant species that remains the reference point for modern botanical nomenclature. This established a standardised binomial or two-part naming scheme where the first name represented the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
and the second identified the
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
within the genus. For the purposes of identification, Linnaeus's ''Systema Sexuale'' classified plants into 24 groups according to the number of their male sexual organs. The 24th group, ''Cryptogamia'', included all plants with concealed reproductive parts, mosses, liverworts, ferns, algae and fungi. Increasing knowledge of
plant anatomy Plant anatomy or phytotomy is the general term for the study of the internal Anatomy, structure of plants. Originally it included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th centu ...
,
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy) Galaxy morphological classification is a system used by astronomers ...
and life cycles led to the realisation that there were more natural affinities between plants than the artificial sexual system of Linnaeus. Adanson (1763),
de Jussieu De Jussieu, the name of a French family which came into prominence towards the close of the sixteenth century, and was known for a century and a half for the botanist Botany, also called , plant biology or phytology, is the science of plant ...
(1789), and Candolle (1819) all proposed various alternative natural systems of classification that grouped plants using a wider range of shared characters and were widely followed. The Candollean system reflected his ideas of the progression of morphological complexity and the later
Bentham & Hooker system A list of systems of plant taxonomy, taxonomic system, the Bentham & Hooker system for seed plants, was published in Bentham and Hooker's ''Genera plantarum ad exemplaria imprimis in herbariis kewensibus servata definita'' in three volumes between ...
, which was influential until the mid-19th century, was influenced by Candolle's approach. Darwin's publication of the ''
Origin of Species ''On the Origin of Species'' (or, more completely, ''On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life''),The book's full original title was ''On the Origin of Species by Me ...
'' in 1859 and his concept of common descent required modifications to the Candollean system to reflect evolutionary relationships as distinct from mere morphological similarity. Botany was greatly stimulated by the appearance of the first "modern" textbook,
Matthias Schleiden Matthias Jakob Schleiden (; 5 April 1804 – 23 June 1881) was a German Botany, botanist and co-founder of cell theory, along with Theodor Schwann and Rudolf Virchow. Career Matthias Jakob Schleiden was born in Hamburg. on 5 April 1804. His fat ...
's ', published in English in 1849 as ''Principles of Scientific Botany''. Schleiden was a microscopist and an early plant anatomist who co-founded the
cell theory In biology, cell theory is a scientific theory first formulated in the mid-nineteenth century, that living organisms are made up of Cell (biology), cells, that they are the basic structural/organizational unit of all organisms, and that all cell ...
with
Theodor Schwann Theodor Schwann (; 7 December 181011 January 1882) was a German physician and physiology, physiologist. His most significant contribution to biology is considered to be the extension of cell theory to animals. Other contributions include the d ...
and
Rudolf Virchow Rudolf Ludwig Carl Virchow (; or ; 13 October 18215 September 1902) was a Germans, German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. He is known as "the father of modern pathology" and as th ...
and was among the first to grasp the significance of the
cell nucleus The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryote, eukaryotic cell (biology), cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as ma ...
that had been described by Robert Brown in 1831. In 1855, Adolf Fick formulated Fick's laws that enabled the calculation of the rates of
molecular diffusion Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of ...
in biological systems.


Late modern botany

Building upon the gene-chromosome theory of heredity that originated with
Gregor Mendel Gregor Johann Mendel, Augustinians, OSA (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a biologist, meteorologist, mathematician, Augustinians, Augustinian friar and abbot of St Thomas's Abbey, Brno, St. Thomas' Abbey in Br ...
(1822–1884),
August Weismann August Friedrich Leopold Weismann FRS (For), HonFRSE, LLD (17 January 18345 November 1914) was a German evolutionary biologist Evolutionary biology is the subfield of biology that studies the evolution, evolutionary processes (natural s ...
(1834–1914) proved that inheritance only takes place through
gamete A gamete (; , ultimately ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also r ...
s. No other cells can pass on inherited characters. The work of Katherine Esau (1898–1997) on plant anatomy is still a major foundation of modern botany. Her books ''Plant Anatomy'' and ''Anatomy of Seed Plants'' have been key plant structural biology texts for more than half a century. The discipline of
plant ecology Plant ecology is a subdiscipline of ecology which studies the distribution and abundance (ecology), abundance of plants, the effects of environmental factors upon the abundance of plants, and the interactions among and between plants and other ...
was pioneered in the late 19th century by botanists such as
Eugenius Warming Eugenius (died 6 September 394) was a usurper in the Western Roman Empire (392–394) against Roman Emperor, Emperor Theodosius I. While Christian himself, Eugenius capitalized on the discontent in the West caused by Theodosius' religious polic ...
, who produced the hypothesis that plants form
communities A community is a Level of analysis, social unit (a group of living things) with commonality such as place (geography), place, Norm (social), norms, religion, values, Convention (norm), customs, or Identity (social science), identity. Communiti ...
, and his mentor and successor Christen C. Raunkiær whose system for describing plant life forms is still in use today. The concept that the composition of plant communities such as temperate broadleaf forest changes by a process of
ecological succession Ecological succession is the process of change in the species structure of an community (ecology), ecological community over time. The time scale can be decades (for example, after a wildfire) or more or less. Bacteria allows for the cycling of ...
was developed by Henry Chandler Cowles,
Arthur Tansley Sir Arthur George Tansley Linnean Society of London, FLS, Fellow of the Royal Society, FRS (15 August 1871 – 25 November 1955) was an England, English botanist and a pioneer in the science of ecology. Educated at Highgate School, University C ...
and
Frederic Clements Frederic Edward Clements (September 16, 1874 – July 26, 1945) was an American plant ecologist and pioneer in the study of plant ecology and vegetation Ecological succession, succession. Biography Born in Lincoln, Nebraska, he studied botany at t ...
. Clements is credited with the idea of climax vegetation as the most complex vegetation that an environment can support and Tansley introduced the concept of
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
s to biology. Building on the extensive earlier work of
Alphonse de Candolle Alphonse Louis Pierre Pyramus (or Pyrame) de Candolle (28 October 18064 April 1893) was a French-Swiss botanist, the son of the Swiss botanist Augustin Pyramus de Candolle. Biography De Candolle, son of Augustin Pyramus de Candolle, first devot ...
,
Nikolai Vavilov Nikolai Ivanovich Vavilov ( rus, Никола́й Ива́нович Вави́лов, p=nʲɪkɐˈlaj ɪˈvanəvʲɪtɕ vɐˈvʲiləf, a=Ru-Nikolay_Ivanovich_Vavilov.ogg; – 26 January 1943) was a Russian and Soviet Union, Soviet agronomi ...
(1887–1943) produced accounts of the
biogeography Biogeography is the study of the distribution of species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as ...
, centres of origin, and evolutionary history of economic plants. Particularly since the mid-1960s there have been advances in understanding of the physics of plant physiological processes such as
transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaf, leaves, Plant stem, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is ...
(the transport of water within plant tissues), the temperature dependence of rates of water
evaporation Evaporation is a type of vaporization that occurs on the surface of a liquid as it changes into the gas phase. High concentration of the evaporating substance in the surrounding gas significantly slows down evaporation, such as when h ...
from the leaf surface and the
molecular diffusion Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of ...
of water vapour and carbon dioxide through stomatal apertures. These developments, coupled with new methods for measuring the size of stomatal apertures, and the rate of
photosynthesis Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemica ...
have enabled precise description of the rates of
gas exchange Gas exchange is the physical process by which gases move passively by Diffusion#Diffusion vs. bulk flow, diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liqui ...
between plants and the atmosphere. Innovations in
statistical analysis Statistical inference is the process of using data analysis to infer properties of an underlying distribution of probability.Upton, G., Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP. . Inferential statistical analysis infers properti ...
by
Ronald Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who a ...
, Frank Yates and others at
Rothamsted Experimental Station Rothamsted Research, previously known as the Rothamsted Experimental Station and then the Institute of Arable Crops Research, is one of the oldest agricultural research institutions in the world, having been founded in 1843. It is located at Harp ...
facilitated rational experimental design and data analysis in botanical research. The discovery and identification of the
auxin Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...
plant hormones Plant hormone (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, from embryogenesis, the regulation of Organ (anatomy), ...
by Kenneth V. Thimann in 1948 enabled regulation of plant growth by externally applied chemicals. Frederick Campion Steward pioneered techniques of
micropropagation Micropropagation or tissue culture is the practice of rapidly multiplying plant stock material to produce many offspring, progeny plants, using modern plant tissue culture methods. Micropropagation is used to multiply a wide variety of plants, ...
and
plant tissue culture Plant tissue culture is a collection of techniques used to maintain or grow plant cells, tissues or organs under sterile conditions on a nutrient culture medium of known composition. It is widely used to produce clones of a plant in a method known ...
controlled by plant hormones. The synthetic auxin 2,4-dichlorophenoxyacetic acid or 2,4-D was one of the first commercial synthetic herbicides. 20th century developments in plant biochemistry have been driven by modern techniques of organic chemical analysis, such as
spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectrum, electromagnetic spectra that result from the interaction between Electromagnetism, electromagnetic radiation and matter as a function of the wavelengt ...
,
chromatography In chemical analysis, chromatography is a laboratory technique for the Separation process, separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it ...
and
electrophoresis Electrophoresis, from Ancient Greek ἤλεκτρον (ḗlektron, "amber") and φόρησις (phórēsis, "the act of bearing"), is the motion of Interface and colloid science, dispersed particles relative to a fluid under the influence of a ...
. With the rise of the related molecular-scale biological approaches of
molecular biology Molecular biology is the branch of biology that seeks to understand the molecule, molecular basis of biological activity in and between Cell (biology), cells, including biomolecule, biomolecular synthesis, modification, mechanisms, and interact ...
,
genomics Genomics is an interdisciplinary field of biology focusing on the structure, function, evolution, mapping, and editing of genomes. A genome is an organism's complete set of DNA, including all of its genes as well as its hierarchical, three-dime ...
,
proteomics Proteomics is the large-scale study of proteins. Proteins are vital parts of living organisms, with many functions such as the formation of structural fibers of muscle tissue, enzymatic digestion of food, or synthesis and replication of DNA. In ...
and
metabolomics Metabolomics is the scientific study of chemical processes involving metabolites, the small molecule substrates, intermediates, and products of cell metabolism. Specifically, metabolomics is the "systematic study of the unique chemical fingerprin ...
, the relationship between the plant
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gene ...
and most aspects of the biochemistry, physiology, morphology and behaviour of plants can be subjected to detailed experimental analysis. The concept originally stated by Gottlieb Haberlandt in 1902 that all plant cells are
totipotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
and can be grown ''in vitro'' ultimately enabled the use of
genetic engineering Genetic engineering, also called genetic modification or genetic manipulation, is the modification and manipulation of an organism's genes using technology. It is a set of Genetic engineering techniques, technologies used to change the gene ...
experimentally to knock out a gene or genes responsible for a specific trait, or to add genes such as GFP that
report A report is a document that presents information in an organized format for a specific audience and purpose. Although summaries of reports may be delivered orally, complete reports are almost always in the form of written documents. Usage In ...
when a gene of interest is being expressed. These technologies enable the biotechnological use of whole plants or plant cell cultures grown in
bioreactors A bioreactor refers to any manufactured device or system that supports a biologically active environment. In one case, a bioreactor is a vessel in which a chemical process In a Process (science), scientific sense, a chemical process is a method ...
to synthesise
pesticides Pesticides are substances that are meant to pest control, control pest (organism), pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microb ...
,
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...
or other
pharmaceuticals A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) is an imp ...
, as well as the practical application of
genetically modified crops Genetically modified crops (GM crops) are plants used in agriculture Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilizat ...
designed for traits such as improved yield. Modern morphology recognises a continuum between the major morphological categories of root, stem (caulome), leaf (phyllome) and
trichome Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...
. Furthermore, it emphasises structural dynamics. Modern systematics aims to reflect and discover phylogenetic relationships between plants. Modern
Molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
largely ignores morphological characters, relying on DNA sequences as data. Molecular analysis of DNA sequences from most families of flowering plants enabled the
Angiosperm Phylogeny Group The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botany, botanists who collaborate to establish a consensus on the Taxonomy (biology), taxonomy of flowering plants (angiosperms) that reflects new knowledge abo ...
to publish in 1998 a
phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among va ...
of flowering plants, answering many of the questions about relationships among
angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
families and species. The theoretical possibility of a practical method for identification of plant species and commercial varieties by
DNA barcoding DNA barcoding is a method of species identification using a short section of DNA from a specific gene or genes. The premise of DNA barcoding is that by comparison with a reference library of such DNA sections (also called "DNA sequence, sequence ...
is the subject of active current research.


Scope and importance

The study of plants is vital because they underpin almost all animal life on Earth by generating a large proportion of the
oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...
and food that provide humans and other organisms with
aerobic respiration Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...
with the chemical energy they need to exist. Plants,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
and
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
are the major groups of organisms that carry out
photosynthesis Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemica ...
, a process that uses the energy of sunlight to convert water and
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon Carbon () is a chemical element with the chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetraval ...
into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. As a by-product of photosynthesis, plants release
oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...
into the atmosphere, a gas that is required by nearly all living things to carry out cellular respiration. In addition, they are influential in the global
carbon Carbon () is a chemical element with the chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—its atom making four electrons available to form covalent bond, covalent chemical bonds. It belongs to gro ...
and
water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
cycles and plant roots bind and stabilise soils, preventing soil
erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust, and then sediment transport, tra ...
. Plants are crucial to the future of human society as they provide food, oxygen, medicine, and products for people, as well as creating and preserving soil. Historically, all living things were classified as either animals or plants and botany covered the study of all organisms not considered animals. Botanists examine both the internal functions and processes within plant
organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structures are parts of cells, as Organ (anatomy), organs are to the ...
s, cells, tissues, whole plants, plant populations and plant communities. At each of these levels, a botanist may be concerned with the classification (
taxonomy Taxonomy is the practice and science of categorization or classification (general theory), classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are ...
),
phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among va ...
and
evolution Evolution is change in the heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes, which are passed on from parent to ...
, structure (
anatomy Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having its ...
and
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy) Galaxy morphological classification is a system used by astronomers ...
), or function (
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying the ...
) of plant life. The strictest definition of "plant" includes only the "land plants" or
embryophytes The Embryophyta (), or land plants, are the most familiar group of green plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all li ...
, which include seed plants (gymnosperms, including the
pines A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family (biology), family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. The World Flora Online created by the Royal Botanic Gardens, Kew and Missouri Botanic ...
, and
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
s) and the free-sporing
cryptogams A cryptogam (scientific name Cryptogamae) is a plant (in the wide sense of the word) or a plant-like organism that reproduces by spore In biology, a spore is a unit of sexual reproduction, sexual or asexual reproduction that may be ada ...
including
fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The Polypodiophyta, polypodiophytes include all living pteridop ...
s,
clubmosses Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...
,
liverworts The Marchantiophyta () are a division of non-vascular plant, non-vascular embryophyte, land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the pla ...
,
hornwort Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have ...
s and
moss Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to ...
es. Embryophytes are multicellular
eukaryote Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...
s descended from an ancestor that obtained its energy from sunlight by
photosynthesis Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemica ...
. They have life cycles with alternating
haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mat ...
and
diploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mat ...
phases. The sexual haploid phase of embryophytes, known as the
gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...
, nurtures the developing diploid embryo
sporophyte A sporophyte () is the diploid multicellular stage in the biological life cycle, life cycle of a plant or alga which produces asexual Spore, spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyt ...
within its tissues for at least part of its life, even in the seed plants, where the gametophyte itself is nurtured by its parent sporophyte. Other groups of organisms that were previously studied by botanists include bacteria (now studied in
bacteriology Bacteriology is the branch and specialty of biology that studies the Morphology (biology), morphology, ecology, genetics and biochemistry of bacteria as well as many other aspects related to them. This subdivision of microbiology involves the identi ...
), fungi (
mycology Mycology is the branch of biology concerned with the study of fungus, fungi, including their genetics, genetic and biochemistry, biochemical properties, their Taxonomy (biology), taxonomy and ethnomycology, their use to humans, including as a so ...
) – including
lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among hypha, filaments of multiple fungus, fungi species in a mutualism (biology), mutualistic relationship.lichenology Lichenology is the branch of mycology Mycology is the branch of biology concerned with the study of fungus, fungi, including their genetics, genetic and biochemistry, biochemical properties, their Taxonomy (biology), taxonomy and ethnomycology ...
), non- chlorophyte
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
(
phycology Phycology () is the scientific study of algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multip ...
), and viruses (
virology Virology is the Scientific method, scientific study of biological viruses. It is a subfield of microbiology that focuses on their detection, structure, classification and evolution, their methods of infection and exploitation of host (biology), ...
). However, attention is still given to these groups by botanists, and fungi (including lichens) and photosynthetic
protist A protist () is any eukaryotic organism (that is, an organism whose Cell (biology), cells contain a cell nucleus) that is not an animal, plant, or fungus. While it is likely that protists share a Common descent, common ancestor (the last eukary ...
s are usually covered in introductory botany courses. Palaeobotanists study ancient plants in the fossil record to provide information about the
evolutionary history of plants The evolution of plants has resulted in a wide range of complexity, from the earliest algal mats, through multicellular marine and freshwater green algae, terrestrial bryophytes, lycopods and ferns, to the complex gymnosperms and angiosperms (fl ...
.
Cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
, the first oxygen-releasing photosynthetic organisms on Earth, are thought to have given rise to the ancestor of plants by entering into an endosymbiotic relationship with an early eukaryote, ultimately becoming the
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
s in plant cells. The new photosynthetic plants (along with their algal relatives) accelerated the rise in atmospheric
oxygen Oxygen is the chemical element with the chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen Group (periodic table), group in the periodic table, a highly Chemical reaction, reactive nonmetal, and an oxidizing a ...
started by the
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
, changing the ancient oxygen-free, reducing, atmosphere to one in which free oxygen has been abundant for more than 2 billion years. Among the important botanical questions of the 21st century are the role of plants as primary producers in the global cycling of life's basic ingredients: energy, carbon, oxygen, nitrogen and water, and ways that our plant stewardship can help address the global environmental issues of
resource management In organizational studies, resource management is the efficient and effective development of an organization's resources when they are needed. Such resources may include the financial resources, inventory, human skills, production resources, or ...
, conservation, human food security, biologically invasive organisms,
carbon sequestration Carbon sequestration is the process of storing carbon in a carbon pool. Carbon dioxide () is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land ...
,
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate variability and change, Climate change in a broader sense also includes ...
, and
sustainability Specific definitions of sustainability are difficult to agree on and have varied in the literature and over time. The concept of sustainability can be used to guide decisions at the global, national, and individual levels (e.g. sustainable livi ...
.


Human nutrition

Virtually all staple foods come either directly from
primary production In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through c ...
by plants, or indirectly from animals that eat them. Plants and other photosynthetic organisms are at the base of most
food chain A food chain is a linear network of links in a food web starting from producer organisms (such as grass or algae which produce their own food via photosynthesis) and ending at an apex predator species (like grizzly bears or killer whales), detr ...
s because they use the energy from the sun and nutrients from the soil and atmosphere, converting them into a form that can be used by animals. This is what ecologists call the first
trophic level The trophic level of an organism is the position it occupies in a food web. A food chain is a succession of organisms that eat other organisms and may, in turn, be eaten themselves. The trophic level of an organism is the number of steps it i ...
. The modern forms of the major
staple food A staple food, food staple, or simply a staple, is a food that is eaten often and in such quantities that it constitutes a dominant portion of a standard Diet (nutrition), diet for a given person or group of people, supplying a large fraction of ...
s, such as
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants o ...
, teff, maize, rice, wheat and other cereal grasses,
pulses In medicine, a pulse represents the tactile arterial palpation of the cardiac cycle (heartbeat) by trained fingertips. The pulse may be palpated in any place that allows an artery to be compressed near the surface of the body, such as at the nec ...
, bananas and plantains, as well as
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants o ...
,
flax Flax, also known as common flax or linseed, is a flowering plant, ''Linum usitatissimum'', in the family Linaceae. It is cultivated as a food and fiber crop in regions of the world with temperate climates. Textiles made from flax are known in W ...
and
cotton Cotton is a soft, fluffy Staple (textiles), staple fiber that grows in a wikt:boll, boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose ...
grown for their fibres, are the outcome of prehistoric selection over thousands of years from among wild ancestral plants with the most desirable characteristics. Botanists study how plants produce food and how to increase yields, for example through
plant breeding Plant breeding is the science of changing the traits of plants in order to produce desired characteristics. It has been used to improve the quality of nutrition in products for humans and animals. The goals of plant breeding are to produce cr ...
, making their work important to humanity's ability to feed the world and provide
food security Food security speaks to the availability of food in a country (or geography) and the ability of individuals within that country (geography) to access, afford, and source adequate foodstuffs. According to the United Nations' Committee on World Fo ...
for future generations. Botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of plant pathogens in agriculture and natural
ecosystems An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
.
Ethnobotany Ethnobotany is the study of a region's plants and their practical uses through the traditional knowledge of a local culture and people. An ethnobotanist thus strives to document the local customs involving the practical uses of local flora for m ...
is the study of the relationships between plants and people. When applied to the investigation of historical plant–people relationships ethnobotany may be referred to as archaeobotany or palaeoethnobotany. Some of the earliest plant-people relationships arose between the
indigenous people Indigenous peoples are culturally distinct ethnic groups whose members are directly descended from the earliest known inhabitants of a particular geographic region and, to some extent, maintain the language and culture of those original people ...
of Canada in identifying edible plants from inedible plants. This relationship the indigenous people had with plants was recorded by ethnobotanists.


Plant biochemistry

Plant biochemistry is the study of the chemical processes used by plants. Some of these processes are used in their primary metabolism like the photosynthetic
Calvin cycle The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...
and
crassulacean acid metabolism Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesis, photosynthesize during the day, but only exchange g ...
. Others make specialised materials like the
cellulose Cellulose is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other ...
and
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...
used to build their bodies, and secondary products like
resin In polymer chemistry and materials science, resin is a solid or highly Viscosity, viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focus ...
s and
aroma compounds An aroma compound, also known as an odorant, aroma, fragrance or flavoring, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficiently Vola ...
.
Plants make various photosynthetic pigments, some of which can be seen here through
paper chromatography Paper chromatography is an analytical method used to separate coloured chemicals or substances. It is now primarily used as a teaching tool, having been replaced in the laboratory A laboratory (; ; colloquially lab) is a facility that provides ...
Xanthophylls
Chlorophyll ''a''
Chlorophyll ''b''
Plants and various other groups of photosynthetic eukaryotes collectively known as "
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
" have unique organelles known as
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
s. Chloroplasts are thought to be descended from
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
that formed endosymbiotic relationships with ancient plant and algal ancestors. Chloroplasts and cyanobacteria contain the blue-green pigment chlorophyll ''a''. Chlorophyll ''a'' (as well as its plant and green algal-specific cousin chlorophyll ''b'') absorbs light in the blue-violet and orange/red parts of the
spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a Continuum (measurement), continuum. The word was first used scientifically in optics to describ ...
while reflecting and transmitting the green light that we see as the characteristic colour of these organisms. The energy in the red and blue light that these pigments absorb is used by chloroplasts to make energy-rich carbon compounds from carbon dioxide and water by
oxygenic photosynthesis Photosynthesis is a process used by plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, ...
, a process that generates
molecular oxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (O2), present at significant levels in Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Gravity of Ea ...
(O2) as a by-product. The light energy captured by chlorophyll ''a'' is initially in the form of electrons (and later a
proton gradient An electrochemical gradient is a gradient of electrochemical potential, usually for an ion that can move across a membrane. The gradient consists of two parts, the chemical gradient, or difference in solute concentration across a membrane, and ...
) that's used to make molecules of ATP and
NADPH Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a Cofactor (biochemistry), cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid synth ...
which temporarily store and transport energy. Their energy is used in the light-independent reactions of the Calvin cycle by the enzyme
rubisco Ribulose-1,5-bisphosphate carboxylase-oxygenase, commonly known by the abbreviations RuBisCo, rubisco, RuBPCase, or RuBPco, is an enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molec ...
to produce molecules of the 3-carbon sugar
glyceraldehyde 3-phosphate Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a metabolite In biochemistry, a metabolite is an intermediate or end product of metabolism. The t ...
(G3P). Glyceraldehyde 3-phosphate is the first product of photosynthesis and the raw material from which
glucose Glucose is a simple sugar with the Chemical formula#Molecular formula, molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis f ...
and almost all other organic molecules of biological origin are synthesised. Some of the glucose is converted to starch which is stored in the chloroplast. Starch is the characteristic energy store of most land plants and algae, while
inulin Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory Common chicory (''Cichorium intybus'') is a somewhat woody, perennial plant, perennial herbaceous pl ...
, a polymer of
fructose Fructose, or fruit sugar, is a ketonic simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbe ...
is used for the same purpose in the sunflower family
Asteraceae The family (biology), family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the Order (biology), order Asterales. Commonly referred to as the aster, daisy, composite, ...
. Some of the glucose is converted to
sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...
(common table sugar) for export to the rest of the plant. Unlike in animals (which lack chloroplasts), plants and their eukaryote relatives have delegated many biochemical roles to their
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
s, including synthesising all their
fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an B ...
, and most
amino acids Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ami ...
. The fatty acids that chloroplasts make are used for many things, such as providing material to build
cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the cytoplasm, interior of all Cell (biology), cells from th ...
s out of and making the polymer
cutin Cutin is one of two waxy polymers that are the main components of the plant cuticle, which covers all aerial surfaces of plants. It is an insoluble substance with waterproof quality. Cutin also harbors cuticular waxes, which assist in cuticle stru ...
which is found in the
plant cuticle A plant cuticle is a protecting film covering the outermost skin layer (epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis ...
that protects land plants from drying out. Plants synthesise a number of unique
polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules called macromolecules, composed of many Repeat unit, repeating subunits. Due to t ...
s like the
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic bond, glycosidic linkages. This carbohydrate c ...
molecules
cellulose Cellulose is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other ...
,
pectin Pectin ( grc, πηκτικός ': "congealed" and "curdled") is a heteropolysaccharide, a structural acid contained in the primary lamella, in the middle lamella, and in the cell walls of terrestrial plants. The principal, chemical component of ...
and
xyloglucan Xyloglucan is a hemicellulose that occurs in the primary cell wall of all vascular plants; however, all enzymes responsible for xyloglucan metabolism are found in Charophyceae algae.LEV Del Bem and M Vincentz (2010) Evolution of xyloglucan-related ...
from which the land plant cell wall is constructed. Vascular land plants make
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...
, a polymer used to strengthen the secondary cell walls of xylem
tracheid A tracheid is a long and tapered Lignin, lignified cell in the xylem of Tracheophyta, vascular plants. It is a type of conductive cell called a tracheary element. Angiosperms use another type of tracheary element, called vessel elements, to trans ...
s and vessels to keep them from collapsing when a plant sucks water through them under water stress. Lignin is also used in other cell types like sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood.
Sporopollenin 270px, SEM image of pollen grains Sporopollenin is one of the most chemically inert biological polymers. It is a major component of the tough outer (exine) walls of plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes ...
is a chemically resistant polymer found in the outer cell walls of spores and pollen of land plants responsible for the survival of early land plant spores and the pollen of seed plants in the fossil record. It is widely regarded as a marker for the start of land plant evolution during the
Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya ...
period. The concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the
Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya ...
and
Silurian The Silurian ( ) is a period (geology), geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (annum, Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortes ...
periods. Many
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
like
maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...
and the
pineapple The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centurie ...
and some dicots like the
Asteraceae The family (biology), family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the Order (biology), order Asterales. Commonly referred to as the aster, daisy, composite, ...
have since independently evolved pathways like
Crassulacean acid metabolism Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions that allows a plant to photosynthesis, photosynthesize during the day, but only exchange g ...
and the carbon fixation pathway for photosynthesis which avoid the losses resulting from
photorespiration Photorespiration (also known as the oxidative photosynthetic carbon cycle or C2 cycle) refers to a process in plant physiology, plant metabolism where the enzyme RuBisCO oxygenates RuBP, wasting some of the energy produced by photosynthesis. The ...
in the more common carbon fixation pathway. These biochemical strategies are unique to land plants.


Medicine and materials

Phytochemistry is a branch of plant biochemistry primarily concerned with the chemical substances produced by plants during
secondary metabolism Secondary metabolism (also called specialized metabolism) is a term for pathways and small molecule products of metabolism that are involved in ecological biological interaction, interactions, but are not absolutely required for the survival of the ...
. Some of these compounds are toxins such as the
alkaloid Alkaloids are a class of base (chemistry), basic, natural product, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Som ...
coniine Coniine is a poisonous chemical compound, an alkaloid present in and isolable from Conium, poison hemlock (''Conium maculatum''), where its presence has been a source of significant economic, medical, and historico-cultural interest; coniine is al ...
from hemlock. Others, such as the
essential oil An essential oil is a concentrated hydrophobic liquid containing Volatility (chemistry), volatile (easily evaporated at normal temperatures) chemical compounds from plants. Essential oils are also known as volatile oils, ethereal oils, aetherol ...
s
peppermint oil Peppermint extract is an herbal extract of peppermint Peppermint (''Mentha'' × ''piperita'') is a Hybrid (biology), hybrid species of Mentha, mint, a cross between Mentha aquatica, watermint and spearmint. Indigenous to Europe and the Middle E ...
and lemon oil are useful for their aroma, as flavourings and spices (e.g.,
capsaicin Capsaicin (8-methyl-''N''-vanillyl-6-nonenamide) ( or ) is an active component of chili peppers, which are plants belonging to the genus ''Capsicum''. It is a chemical Irritation, irritant for mammals, including humans, and produces a sensation ...
), and in medicine as pharmaceuticals as in
opium Opium (or poppy tears, scientific name: ''Lachryma papaveris'') is dried latex obtained from the seed Capsule (fruit), capsules of the opium poppy ''Papaver somniferum''. Approximately 12 percent of opium is made up of the analgesic alkaloid m ...
from
opium poppies Opium (or poppy tears, scientific name: ''Lachryma papaveris'') is dried latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latexes are found in nature, but synthetic latexes are common as well. In natur ...
. Many
medicinal Medicine is the science and Praxis (process), practice of caring for a patient, managing the diagnosis, prognosis, Preventive medicine, prevention, therapy, treatment, Palliative care, palliation of their injury or disease, and Health promotion ...
and
recreational drugs Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for happiness, enjoyment, amusement, ...
, such as
tetrahydrocannabinol Tetrahydrocannabinol (THC) is the principal psychoactive drug, psychoactive constituent of cannabis and one of at least 113 total cannabinoids identified on the plant. Although the chemical formula for THC (C21H30O2) describes multiple Isomer, ...
(active ingredient in
cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: ''Cannabis sativa'', ''Cannabis indica, C. indica'', and ''Cannabis ruderalis, ...
),
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordi ...
,
morphine Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies (''Papaver somniferum''). It is mainly used as a analgesic, pain medication, and is also commonly used recreational drug, recreationally, or to make ...
and
nicotine Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As ...
come directly from plants. Others are simple derivatives of botanical natural products. For example, the pain killer
aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat inc ...
is the acetyl
ester In chemistry, an ester is a chemical compound, compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an Alcohol ...
of
salicylic acid Salicylic acid is an organic compound with the formula HOC6H4CO2H. A colorless, bitter-tasting solid, it is a precursor to and a active metabolite, metabolite of aspirin (acetylsalicylic acid). It is a plant hormone, and has been listed by the ...
, originally isolated from the bark of
willow Willows, also called sallows and osiers, from the genus ''Salix'', comprise List of Salix species, around 400 speciesMabberley, D.J. 1997. The Plant Book, Cambridge University Press #2: Cambridge. of typically deciduous trees and shrubs, found ...
trees, and a wide range of
opiate An opiate, in classical pharmacology, is a substance derived from opium Opium (or poppy tears, scientific name: ''Lachryma papaveris'') is dried latex obtained from the seed Capsule (fruit), capsules of the opium poppy ''Papaver somniferu ...
painkillers An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of Pharmaceutical drug, drugs used to achieve relief from pain (that is, analgesia or p ...
like
heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a potent opioid mainly used as a recreational drug for its euphoric effects. Medical grade diamorphine is used as a pure hydrochloride salt. Various white and brown ...
are obtained by chemical modification of
morphine Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies (''Papaver somniferum''). It is mainly used as a analgesic, pain medication, and is also commonly used recreational drug, recreationally, or to make ...
obtained from the
opium poppy ''Papaver somniferum'', commonly known as the opium poppy or breadseed poppy, is a species of flowering plant in the family Papaveraceae. It is the species of plant from which both opium and poppy seeds are derived and is also a valuable ornamen ...
. Popular
stimulant Stimulants (also often referred to as psychostimulants or colloquially as uppers) is an overarching term that covers many drugs including those that increase activity of the central nervous system and the body, drugs that are pleasurable and inv ...
s come from plants, such as
caffeine Caffeine is a central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordi ...
from coffee, tea and chocolate, and
nicotine Nicotine is a natural product, naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and ''Duboisia hopwoodii'') and is widely used recreational drug use, recreationally as a stimulant and anxiolytic. As ...
from tobacco. Most alcoholic beverages come from
fermentation Fermentation is a metabolism, metabolic process that produces chemical changes in organic Substrate (chemistry), substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in ...
of
carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or may ...
-rich plant products such as
barley Barley (''Hordeum vulgare''), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains, particularly in Eurasia Eurasia (, ) is the largest continental area o ...
(beer), rice (
sake Sake, also spelled saké ( ; also referred to as Japanese rice wine), is an alcoholic beverage of Japanese Japanese may refer to: * Something from or related to Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is a ...
) and grapes (wine). Native Americans have used various plants as ways of treating illness or disease for thousands of years. This knowledge Native Americans have on plants has been recorded by enthnobotanists and then in turn has been used by pharmaceutical companies as a way of
drug discovery In the fields of medicine, biotechnology and pharmacology, drug discovery is the process by which new candidate pharmaceutical drug, medications are discovered. Historically, drugs were discovered by identifying the active ingredient from tradit ...
. Plants can synthesise useful coloured dyes and pigments such as the
anthocyanin Anthocyanins (), also called anthocyans, are water-soluble vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart gave the name Anthokyan to a chemical com ...
s responsible for the red colour of
red wine Red wine is a type of wine made from dark-colored grape varieties. The Wine color, color of the wine can range from intense violet, typical of young wines, through to brick red for mature wines and brown for older red wines. The juice from most ...
, yellow weld and blue
woad ''Isatis tinctoria'', also called woad (), dyer's woad, or glastum, is a flowering plant in the family Brassicaceae (the mustard family) with a documented history of use as a blue dye and medicinal plant. Its genus name, Isatis, derives from ...
used together to produce
Lincoln green Lincoln Green is a mainly residential area of Leeds, West Yorkshire, England around Lincoln Green Road, and is adjacent to and southwest of St James's University Hospital. It falls within the Burmantofts and Richmond Hill ward of the City of ...
,
indoxyl In chemistry, indoxyl is a nitrogenous substance with the chemical formula: C8H7NO. Indoxyl is isomeric with oxindol and is obtained as an oily liquid. Indoxyl is obtained from indican, which is a glycoside. The hydrolysis of indican yields β-D- ...
, source of the blue dye
indigo Indigo is a deep color close to the Shades of blue#Blue (RGB) (X11 blue), color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine, based on the indigo dye, ancient dye of the same name. The word " ...
traditionally used to dye denim and the artist's pigments
gamboge Gamboge ( , ) is a partially transparent deep Saffron (colour), saffron to mustard yellow pigment.Other forms and spellings are: cambodia, cambogium, camboge, cambugium, gambaugium, gambogia, gambozia, gamboidea, gambogium, gumbouge, gambouge, ga ...
and
rose madder Rose madder (also known as madder) is a red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometre 330px, ...
. Sugar,
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, ...
, cotton,
linen Linen () is a textile made from the fibers of the flax plant. Linen is very strong, absorbent, and dries faster than cotton. Because of these properties, linen is comfortable to wear in hot weather and is valued for use in garments. It also h ...
,
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial or medicinal use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest growing plants o ...
, some types of
rope A rope is a group of yarns, Plying, plies, fibres, or strands that are twisted or braided together into a larger and stronger form. Ropes have tensile strength and so can be used for dragging and lifting. Rope is thicker and stronger than simi ...
, wood and
particle board Particle board, also known as chipboard or low-density fiberboard, is an engineered wood product manufactured from wood chips and a synthetic resin or other suitable binder, which is pressed and Extrusion, extruded. Particle board is often confus ...
s,
papyrus Papyrus ( ) is a material similar to thick paper that was used in ancient times as a writing surface. It was made from the pith of the papyrus plant, ''Cyperus papyrus'', a wetland sedge. ''Papyrus'' (plural: ''papyri'') can also refer to a do ...
and paper,
vegetable oil Vegetable oils, or vegetable fats, are oils extracted from seeds or from other parts of fruits. Like animal fats, vegetable fats are ''mixtures'' of triglycerides. Soybean oil, grape seed oil, and cocoa butter are examples of seed oils, or fats ...
s, wax, and
natural rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...
are examples of commercially important materials made from plant tissues or their secondary products.
Charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, cal ...
, a pure form of carbon made by
pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek language, Greek-derived ...
of wood, has a long
history History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as we ...
as a metal-
smelting Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including Silver mining#Ore processing, silver, iron-making, iron, copper extracti ...
fuel, as a filter material and
adsorbent Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a Surface science, surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorpti ...
and as an artist's material and is one of the three ingredients of
gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, carbon (in the form of charcoal) and potassium nitrate (saltpeter). Th ...
.
Cellulose Cellulose is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other ...
, the world's most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. Products made from cellulose include
rayon Rayon is a semi-synthetic fiber, made from natural sources of regenerated cellulose fiber, cellulose, such as wood and related agricultural products. It has the same molecular structure as cellulose. It is also called viscose. Many types and gr ...
and
cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, Fat, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coat ...
,
wallpaper paste file:Wallpaper paste flakes.JPG, Adhesive flakes that are mixed with water to produce wallpaper paste Wallpaper adhesive or wallpaper paste is a specific adhesive, based on modified starch, methylcellulose, or clay used to fix wallpaper to walls. ...
,
biobutanol image:Butanol_flat_structure.png, 220px, Butanol, a C-4 hydrocarbon is a promising bio-derived fuel, which shares many properties with gasoline. Butanol may be used as a fuel in an internal combustion engine. It is more similar to gasoline than it ...
and gun cotton.
Sugarcane Sugarcane or sugar cane is a species of (often hybrid) tall, Perennial plant, perennial grass (in the genus ''Saccharum'', tribe Andropogoneae) that is used for sugar Sugar industry, production. The plants are 2–6 m (6–20 ft) tall with ...
,
rapeseed Rapeseed (''Brassica napus ''subsp.'' napus''), also known as rape, or oilseed rape, is a bright-yellow flowering member of the family Brassicaceae (mustard or cabbage family), cultivated mainly for its oil-rich seed, which naturally contains a ...
and
soy The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume native to East Asia, widely grown for its edible bean, which has numerous uses. Traditional unfermented food uses of soybeans include soy milk, from which tofu and ...
are some of the plants with a highly fermentable sugar or oil content that are used as sources of
biofuel Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels, such as oil. According to the United States Energy Information Administration (EIA ...
s, important alternatives to
fossil fuel A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and combustion, burned as a fuel. The main fossil fuels are coal, petroleum, oil, and natura ...
s, such as
biodiesel Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat (tallow), soybean oil, or some other vegetable oil with ...
. Sweetgrass was used by Native Americans to ward off bugs like
mosquito Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small Diptera, flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish ...
es. These bug repelling properties of sweetgrass were later found by the
American Chemical Society The American Chemical Society (ACS) is a scientific society based in the United States that supports scientific inquiry in the field of chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a na ...
in the molecules phytol and
coumarin Coumarin () or 2''H''-chromen-2-one is an aromatic organic chemical compound with formula . Its molecule can be described as a benzene molecule with two adjacent hydrogen atoms replaced by a lactone-like chain , forming a second six-membered h ...
.


Plant ecology

Plant ecology is the science of the functional relationships between plants and their
habitat In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
s – the environments where they complete their life cycles. Plant ecologists study the composition of local and regional
flora Flora is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. Sometimes bacteria and fungi are also referred to as flora, as in the terms '' ...
s, their
biodiversity Biodiversity or biological diversity is the variety and variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem d ...
, genetic diversity and fitness, the
adaptation In biology, adaptation has three related meanings. Firstly, it is the dynamic evolutionary process of natural selection that fits organisms to their environment, enhancing their Fitness (biology), evolutionary fitness. Secondly, it is a stat ...
of plants to their environment, and their competitive or mutualistic interactions with other species. Some ecologists even rely on
empirical data Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence is of central importance to the sciences and ...
from indigenous people that is gathered by ethnobotanists. This information can relay a great deal of information on how the land once was thousands of years ago and how it has changed over that time. The goals of plant ecology are to understand the causes of their distribution patterns, productivity, environmental impact, evolution, and responses to environmental change. Plants depend on certain
edaphic Edaphology (from Greek , ''edaphos'', "ground",, '' -logia'') is concerned with the influence of soils on living beings, particularly plants. It is one of two main divisions of soil science, the other being pedology. Edaphology includes the s ...
(soil) and climatic factors in their environment but can modify these factors too. For example, they can change their environment's
albedo Albedo (; ) is the measure of the diffuse reflection of sunlight, solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body ...
, increase
runoff Runoff, run-off or RUNOFF may refer to: * RUNOFF, the first computer text-formatting program * Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed * Runoff or run-off, a stock marke ...
interception, stabilise mineral soils and develop their organic content, and affect local temperature. Plants compete with other organisms in their
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
for resources. They interact with their neighbours at a variety of spatial scales in groups, populations and
communities A community is a Level of analysis, social unit (a group of living things) with commonality such as place (geography), place, Norm (social), norms, religion, values, Convention (norm), customs, or Identity (social science), identity. Communiti ...
that collectively constitute vegetation. Regions with characteristic vegetation types and dominant plants as well as similar
abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and Physical property, physical parts of the Natural environment, environment that affect living organisms and the functioning of ecosystems. Abiotic factors and ...
and biotic factors,
climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...
, and
geography Geography (from Ancient Greek, Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, i ...
make up
biomes A biome () is a biogeographical unit consisting of a biological community A community is a social unit (a group of living things) with commonality such as place, norms, religion Religion is usually defined as a social- cultural syst ...
like
tundra In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian language, Russian (') from the Kildin Sámi language, Kildin Sámi wo ...
or
tropical rainforest Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as ''lowland equatori ...
.
Herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...
s eat plants, but plants can defend themselves and some species are
parasitic Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted structurally to this way of lif ...
or even
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, adipose tissue, f ...
. Other organisms form mutually beneficial relationships with plants. For example,
mycorrhiza   A mycorrhiza (from Ancient Greek, Greek μύκης ', "fungus", and ῥίζα ', "root"; pl. mycorrhizae, mycorrhiza or mycorrhizas) is a symbiosis, symbiotic association between a fungus and a plant. The term mycorrhiza refers to the role ...
l fungi and
rhizobia Rhizobia are diazotrophic bacteria that Nitrogen fixation, fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant Host (biology), host; they cannot i ...
provide plants with nutrients in exchange for food,
ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...
s are recruited by ant plants to provide protection,
honey bee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the current cosmop ...
s,
bat Bats are mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a ...
s and other animals pollinate flowers and
humans Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedality, bipedalism and exceptional cognitive skills due to a large and complex Human brain, brain. This has enabled the development of ad ...
and other animals act as
dispersal vector A dispersal vector is an agent of biological dispersal that moves a dispersal unit, or organism, away from its birth population to another location or population in which the individual will reproduce. These dispersal units can range from pollen to ...
s to spread
spore In biology, a spore is a unit of sexual reproduction, sexual or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of ...
s and
seed A seed is an Plant embryogenesis, embryonic plant enclosed in a testa (botany), protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, includ ...
s.


Plants, climate and environmental change

Plant responses to climate and other environmental changes can inform our understanding of how these changes affect ecosystem function and productivity. For example, plant
phenology Phenology is the study of periodic events in biological life cycle In biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent ...
can be a useful
proxy Proxy may refer to: * Proxy or agent (law), a substitute authorized to act for another entity or a document which authorizes the agent so to act * Proxy (climate), a measured variable used to infer the value of a variable of interest in climate re ...
for temperature in historical climatology, and the biological impact of climate change and
global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate variability and change, Climate change in a broader sense also includes ...
.
Palynology Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and ''-logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposits ...
, the analysis of fossil pollen deposits in sediments from thousands or millions of years ago allows the reconstruction of past climates. Estimates of atmospheric concentrations since the
Palaeozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic The Phanerozoic Eon is the current geologic eon in the geologic time scale The geologic time scale, or geological time scale, (GTS) is a repr ...
have been obtained from stomatal densities and the leaf shapes and sizes of ancient
land plants The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...
.
Ozone depletion Ozone depletion consists of two related events observed since the late 1970s: a steady lowering of about four percent in the total amount of ozone in Earth, Earth's atmosphere, and a much larger springtime decrease in stratospheric ozone (the ozo ...
can expose plants to higher levels of ultraviolet radiation-B (UV-B), resulting in lower growth rates. Moreover, information from studies of
community ecology In ecology, a community is a group or association (ecology), association of Population ecology, populations of two or more different species occupying the same geographical area at the same time, also known as a biocoenosis, biotic community, ...
, plant
systematics Biological systematics is the study of the diversification of living forms, both past and present, and the Correlation and dependence, relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: c ...
, and
taxonomy Taxonomy is the practice and science of categorization or classification (general theory), classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are ...
is essential to understanding vegetation change,
habitat destruction Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...
and species extinction.


Genetics

Inheritance in plants follows the same fundamental principles of genetics as in other multicellular organisms.
Gregor Mendel Gregor Johann Mendel, Augustinians, OSA (; cs, Řehoř Jan Mendel; 20 July 1822 – 6 January 1884) was a biologist, meteorologist, mathematician, Augustinians, Augustinian friar and abbot of St Thomas's Abbey, Brno, St. Thomas' Abbey in Br ...
discovered the genetic laws of inheritance by studying inherited traits such as shape in ''Pisum sativum'' (
peas The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...
). What Mendel learned from studying plants has had far-reaching benefits outside of botany. Similarly, " jumping genes" were discovered by
Barbara McClintock Barbara McClintock (June 16, 1902 – September 2, 1992) was an American scientist and cytogenetics, cytogeneticist who was awarded the 1983 Nobel Prize in Physiology or Medicine. McClintock received her PhD in botany from Cornell University in ...
while she was studying maize. Nevertheless, there are some distinctive genetic differences between plants and other organisms. Species boundaries in plants may be weaker than in animals, and cross species hybrids are often possible. A familiar example is
peppermint Peppermint (''Mentha'' × ''piperita'') is a Hybrid (biology), hybrid species of Mentha, mint, a cross between Mentha aquatica, watermint and spearmint. Indigenous to Europe and the Middle East, the plant is now widely spread and cultivated in m ...
, ''Mentha'' × ''piperita'', a sterile hybrid between ''
Mentha aquatica ''Mentha aquatica'' (water mint; syn. ''Mentha hirsuta'' Huds.Euro+Med Plantbase Project''Mentha aquatica'') is a perennial plant, perennial flowering plant in the Mentha, mint family Lamiaceae. It grows in moist places and is native to much of ...
'' and spearmint, ''
Mentha spicata Spearmint, also known as garden mint, common mint, lamb mint and mackerel mint, is a species of Mentha, mint, ''Mentha spicata'' (, native to Europe and southern temperate Asia, extending from Ireland in the west to southern China in the east. I ...
''. The many cultivated varieties of wheat are the result of multiple inter- and intra- specific crosses between wild species and their hybrids.
Angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
with
monoecious Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...
flowers often have self-incompatibility mechanisms that operate between the
pollen Pollen is a powdery substance produced by Spermatophyte, seed plants. It consists of pollen grains (highly reduced microgametophytes), which produce male gametes (sperm cells). Pollen grains have a hard coat made of sporopollenin that protects ...
and stigma so that the pollen either fails to reach the stigma or fails to
germinate Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an flowering plant, angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spor ...
and produce male
gamete A gamete (; , ultimately ) is a Ploidy#Haploid and monoploid, haploid cell that fuses with another haploid cell during fertilization in organisms that Sexual reproduction, reproduce sexually. Gametes are an organism's reproductive cells, also r ...
s. This is one of several methods used by plants to promote
outcrossing Out-crossing or out-breeding is the technique of crossing between different breeds. This is the practice of introducing distantly related genetic material into a breeding line, thereby increasing genetic diversity. Outcrossing can be a useful ...
. In many land plants the male and female gametes are produced by separate individuals. These species are said to be
dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in Spermatophyte, seed plants). Dioeci ...
when referring to vascular plant
sporophyte A sporophyte () is the diploid multicellular stage in the biological life cycle, life cycle of a plant or alga which produces asexual Spore, spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyt ...
s and
dioicous Dioicy () is a sexual system where Archegonium, archegonia and Antheridium, antheridia are produced on separate Gametophyte, gametophytes. It is one of the two main sexual systems in Bryophyte, bryophytes. Both dioicous () and Monoicy, monoicous ...
when referring to
bryophyte The Bryophyta s.l. are a proposed taxonomic division containing three groups of non-vascular land plants (embryophytes): the liverworts, hornworts and moss Mosses are small, non-vascular flower A flower, sometimes known as a bloo ...
gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...
s. Unlike in higher animals, where
parthenogenesis Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and development ...
is rare,
asexual reproduction Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the ...
may occur in plants by several different mechanisms. The formation of stem
tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing s ...
s in potato is one example. Particularly in
arctic The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenland), northern Finland ...
or alpine habitats, where opportunities for fertilisation of flowers by animals are rare, plantlets or
bulbs In botany, a bulb is structurally a short Plant stem, stem with fleshy leaf, leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food st ...
, may develop instead of flowers, replacing
sexual reproduction Sexual reproduction is a type of reproduction that involves a complex Biological life cycle, life cycle in which a gamete (haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to p ...
with asexual reproduction and giving rise to clonal populations genetically identical to the parent. This is one of several types of
apomixis In botany, apomixis is asexual reproduction without fertilization. Its etymology is Greek for "away from" + "mixing". This definition notably does not mention meiosis. Thus "normal Plant reproduction#Asexual reproduction, asexual reproduction" o ...
that occur in plants. Apomixis can also happen in a
seed A seed is an Plant embryogenesis, embryonic plant enclosed in a testa (botany), protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, includ ...
, producing a seed that contains an embryo genetically identical to the parent. Most sexually reproducing organisms are diploid, with paired chromosomes, but doubling of their
chromosome number Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mat ...
may occur due to errors in
cytokinesis Cytokinesis () is the part of the cell division biological process, process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of Mitosis, nuclear d ...
. This can occur early in development to produce an autopolyploid or partly autopolyploid organism, or during normal processes of cellular differentiation to produce some cell types that are polyploid ( endopolyploidy), or during gamete formation. An allopolyploid plant may result from a hybridisation event between two different species. Both autopolyploid and allopolyploid plants can often reproduce normally, but may be unable to cross-breed successfully with the parent population because there is a mismatch in chromosome numbers. These plants that are
reproductively isolated The mechanisms of reproductive isolation are a collection of evolutionary mechanisms, ethology, behaviors and physiology, physiological processes critical for speciation. They prevent members of different species from producing offspring, or ensu ...
from the parent species but live within the same geographical area, may be sufficiently successful to form a new
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
. Some otherwise sterile plant polyploids can still reproduce
vegetatively Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or Cutting (plant), cutting of the paren ...
or by seed apomixis, forming clonal populations of identical individuals.
Durum Durum wheat (), also called pasta wheat or macaroni wheat (''Triticum durum'' or ''Triticum turgidum'' subsp. ''durum''), is a Polyploid, tetraploid species of wheat. It is the second most cultivated species of wheat after common wheat, although ...
wheat is a fertile
tetraploid Polyploidy is a condition in which the cells of an organism In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by ...
allopolyploid, while bread wheat is a fertile
hexaploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei ( eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set cont ...
. The commercial banana is an example of a sterile, seedless
triploid Polyploidy is a condition in which the biological cell, cells of an organism have more than one pair of (Homologous chromosome, homologous) chromosomes. Most species whose cells have Cell nucleus, nuclei (eukaryotes) are diploid, meaning they ha ...
hybrid. Common dandelion is a triploid that produces viable seeds by apomictic seed. As in other eukaryotes, the inheritance of endosymbiotic organelles like
mitochondria A mitochondrion (; ) is an organelle found in the cells of most Eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which i ...
and
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
s in plants is non-
Mendelian Mendelian inheritance (also known as Mendelism) is a type of biology, biological Heredity, inheritance following the principles originally proposed by Gregor Mendel in 1865 and 1866, re-discovered in 1900 by Hugo de Vries and Carl Correns, an ...
. Chloroplasts are inherited through the male parent in gymnosperms but often through the female parent in flowering plants.


Molecular genetics

A considerable amount of new knowledge about plant function comes from studies of the molecular genetics of model plants such as the Thale cress, ''
Arabidopsis thaliana ''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small flowering plant native to Eurasia and Africa. ''A. thaliana'' is considered a weed; it is found along the shoulders of roads and in disturbed land. A winter an ...
'', a weedy species in the mustard family (
Brassicaceae Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important Family (biology), family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some ar ...
). The
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding gene ...
or hereditary information contained in the genes of this species is encoded by about 135 million
base pairs A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
of DNA, forming one of the smallest genomes among
flowering plant Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
s. ''Arabidopsis'' was the first plant to have its genome sequenced, in 2000. The sequencing of some other relatively small genomes, of rice (''
Oryza sativa ''Oryza sativa'', commonly known as Asian rice or indica rice, is the plant species most commonly referred to in English as ''rice''. It is the List of rice cultivars, type of farmed rice whose cultivars are most common globally, and History of ...
'') and ''
Brachypodium distachyon ''Brachypodium distachyon'', commonly called purple false brome or stiff brome, is a Poaceae, grass species native to southern Europe, northern Africa and southwestern Asia east to India. It is related to the major cereal grain species wheat, bar ...
'', has made them important model species for understanding the genetics, cellular and molecular biology of
cereals A cereal is any Poaceae, grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, Cereal germ, germ, and bran. Cereal Grain, grain crops are grown in greater quantit ...
,
grasses Poaceae () or Gramineae () is a large and nearly ubiquitous Family (biology), family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species culti ...
and
monocots Monocotyledons (), commonly referred to as monocots, (Lilianae ''sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. Th ...
generally. Model plants such as ''Arabidopsis thaliana'' are used for studying the molecular biology of
plant cell Plant cells are the cells present in Viridiplantae, green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids ...
s and the
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
. Ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. Corn has been used to study mechanisms of
photosynthesis Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemica ...
and
phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
loading of sugar in plants. The single celled
green alga The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...
''
Chlamydomonas reinhardtii ''Chlamydomonas reinhardtii'' is a single-cell green alga about 10 micrometre The micrometre (American and British English spelling differences#-re, -er, international spelling as used by the International Bureau of Weights and Measures ...
'', while not an
embryophyte The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...
itself, contains a green-pigmented
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
related to that of land plants, making it useful for study. A
red alga Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...
'' Cyanidioschyzon merolae'' has also been used to study some basic chloroplast functions.
Spinach Spinach (''Spinacia oleracea'') is a Leaf vegetable, leafy green flowering plant native to Central Asia, central and western Asia. It is of the order Caryophyllales, family Amaranthaceae, subfamily Chenopodioideae. Its leaves are a common edible ...
,
peas The pea is most commonly the small spherical seed or the seed-pod of the flowering plant species ''Pisum sativum''. Each pod contains several peas, which can be green or yellow. Botanically, pea pods are fruit, since they contain seeds and d ...
,
soybeans The soybean, soy bean, or soya bean (''Glycine max'') is a species of legume A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. ...
and a moss ''
Physcomitrella patens ''Physcomitrium patens'', (synonym: ''Physcomitrella patens'' ) the spreading earthmoss, is a moss (bryophyte) used as a model organism for studies on plant evolution, development, and physiology. Distribution and ecology ''Physcomitrella pat ...
'' are commonly used to study plant cell biology. '' Agrobacterium tumefaciens'', a soil
rhizosphere The rhizosphere is the narrow region of soil or Substrate (biology), substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Pore space in soil, Soil pores in the rhizosphere can ...
bacterium, can attach to plant cells and infect them with a
callus A callus is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may o ...
-inducing
Ti plasmid A tumour inducing (Ti) plasmid is a plasmid found in pathogenic species of ''Agrobacterium'', including Agrobacterium tumefaciens, ''A. tumefaciens, Rhizobium rhizogenes, ''A. rhizogenes'', ''A. rubi'' and Allorhizobium vitis, ''A. vitis''. Evolu ...
by
horizontal gene transfer Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between Unicellular organism, unicellular and/or multicellular organisms other than by the ("vertical") transmission of DNA from parent to offsprin ...
, causing a callus infection called crown gall disease. Schell and Van Montagu (1977) hypothesised that the Ti plasmid could be a natural vector for introducing the
Nif gene The ''nif'' genes are genes encoding enzymes involved in the nitrogen fixation, fixation of atmospheric nitrogen into a form of nitrogen available to living organisms. The primary enzyme encoded by the ''nif'' genes is the nitrogenase complex which ...
responsible for
nitrogen fixation Nitrogen fixation is a chemical process by which molecular nitrogen (), with a strong triple covalent bond, in the Atmosphere of Earth, air is converted into ammonia () or related nitrogenous compounds, typically in soil or aquatic systems but al ...
in the root nodules of
legumes A legume () is a plant in the family Fabaceae (or Leguminosae), or the fruit or seed of such a plant. When used as a dry grain, the seed is also called a pulse. Legumes are grown agriculturally, primarily for human consumption, for livestock for ...
and other plant species. Today, genetic modification of the Ti plasmid is one of the main techniques for introduction of
transgene A transgene is a gene that has been transferred naturally, or by any of a number of genetic engineering techniques, from one organism to another. The introduction of a transgene, in a process known as transgenesis, has the potential to change the ...
s to plants and the creation of
genetically modified crops Genetically modified crops (GM crops) are plants used in agriculture Agriculture or farming is the practice of cultivating Plant, plants and livestock. Agriculture was the key development in the rise of Sedentism, sedentary human civilizat ...
.


Epigenetics

Epigenetics In biology, epigenetics is the study of stable phenotypic changes (known as ''marks'') that do not involve alterations in the DNA sequence. The Ancient Greek, Greek prefix ''wikt:epi-, epi-'' ( "over, outside of, around") in ''epigenetics'' imp ...
is the study of heritable changes in gene function that cannot be explained by changes in the underlying
DNA sequence DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. The ...
but cause the organism's genes to behave (or "express themselves") differently. One example of epigenetic change is the marking of the genes by
DNA methylation DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. When located in a gene promoter (genetics), promoter, DNA methylati ...
which determines whether they will be expressed or not. Gene expression can also be controlled by repressor proteins that attach to silencer regions of the DNA and prevent that region of the DNA code from being expressed. Epigenetic marks may be added or removed from the DNA during programmed stages of development of the plant, and are responsible, for example, for the differences between anthers, petals and normal leaves, despite the fact that they all have the same underlying genetic code. Epigenetic changes may be temporary or may remain through successive
cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...
s for the remainder of the cell's life. Some epigenetic changes have been shown to be
heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cell (biology), cells or orga ...
, while others are reset in the germ cells. Epigenetic changes in
eukaryotic Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...
biology serve to regulate the process of
cellular differentiation Cellular differentiation is the process in which a stem cell alters from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular ...
. During
morphogenesis Morphogenesis (from the Greek language, Greek ''morphê'' shape and ''genesis'' creation, literally "the generation of form") is the biological process that causes a Cell (biology), cell, Tissue (biology), tissue or organism to develop its shape. ...
,
totipotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
stem cells In multicellular organisms, stem cells are Cellular differentiation, undifferentiated or partially differentiated Cell (biology), cells that can differentiate into various types of cells and Cell proliferation, proliferate indefinitely to produc ...
become the various
pluripotent Pluripotency: These are the cells that can generate into any of the three Germ layers which imply Endodermal, Mesodermal, and Ectodermal cells except tissues like the placenta. According to Latin terms, Pluripotentia means the ability for many thin ...
cell line An immortalised cell line is a population of cell (biology), cells from a multicellular organism which would normally not proliferate indefinitely but, due to mutation, have evaded normal cellular senescence and instead can keep undergoing divi ...
s of the
embryo An embryo is an initial stage of development of a multicellular organism. In organisms that Sexual reproduction, reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell ...
, which in turn become fully differentiated cells. A single fertilised egg cell, the
zygote A zygote (, ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual ...
, gives rise to the many different
plant cell Plant cells are the cells present in Viridiplantae, green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids ...
types including
parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word π ...
, xylem vessel elements,
phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
sieve tubes,
guard cell Guard cells are specialized plant cells in the epidermis of leaves, stems and other organs that are used to control gas exchange. They are produced in pairs with a gap between them that forms a stoma, stomatal pore. The stomatal pores are largest ...
s of the
epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...
, etc. as it continues to divide. The process results from the epigenetic activation of some genes and inhibition of others. Unlike animals, many plant cells, particularly those of the
parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word π ...
, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. Exceptions include highly lignified cells, the
sclerenchyma The ground tissue of plants includes all tissues that are neither dermal The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primaril ...
and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. While plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. Epigenetic changes can lead to paramutations, which do not follow the Mendelian heritage rules. These epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other.


Plant evolution

The
chloroplast A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...
s of plants have a number of biochemical, structural and genetic similarities to
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
, (commonly but incorrectly known as "blue-green algae") and are thought to be derived from an ancient endosymbiotic relationship between an ancestral
eukaryotic cell Eukaryotes () are organisms whose Cell (biology), cells have a cell nucleus, nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the ...
and a cyanobacterial resident. The
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
are a
polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as Homoplasy, homoplasies, which are explained as a result ...
group and are placed in various divisions, some more closely related to plants than others. There are many differences between them in features such as cell wall composition, biochemistry, pigmentation, chloroplast structure and nutrient reserves. The algal division
Charophyta Charophyta () is a group of freshwater green algae, called charophytes (), sometimes treated as a phylum, division, yet also as a superdivision or an unranked clade. The terrestrial plants, the Embryophyta emerged within Charophyta, possibly fro ...
, sister to the green algal division
Chlorophyta Chlorophyta or Prasinophyte, Prasinophyta is a taxon of green algae informally called chlorophytes. The name is used in two very different senses, so care is needed to determine the use by a particular author. In older classification systems, i ...
, is considered to contain the ancestor of true plants. The Charophyte class
Charophyceae Charophyceae is a Class (biology), class of Charophyta, charophyte green algae. AlgaeBase places it in division Charophyta. Extant (living) species are placed in a single order Charales, commonly known as "stoneworts" and "brittleworts". Fossil m ...
and the land plant sub-kingdom
Embryophyta The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...
together form the
monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population Population typically refers to the number of ...
group or clade Streptophytina. Nonvascular land plants are
embryophyte The Embryophyta (), or land plants, are the most familiar group of green plants that comprise vegetation on Earth. Embryophytes () have a common ancestor with green algae, having emerged within the Phragmoplastophyta clade of green algae as siste ...
s that lack the vascular tissues
xylem Xylem is one of the two types of transport tissue in vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of embryophyte, land plants ( accepted known species) that have lignin, ...
and
phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
. They include
moss Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to ...
es,
liverworts The Marchantiophyta () are a division of non-vascular plant, non-vascular embryophyte, land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the pla ...
and
hornwort Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have ...
s. Pteridophytic vascular plants with true xylem and phloem that reproduced by spores germinating into free-living gametophytes evolved during the Silurian period and diversified into several lineages during the late
Silurian The Silurian ( ) is a period (geology), geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (annum, Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortes ...
and early
Devonian The Devonian ( ) is a period (geology), geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Dev ...
. Representatives of the lycopods have survived to the present day. By the end of the Devonian period, several groups, including the
lycopods Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...
, sphenophylls and
progymnosperm The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the trimerophyte Trimerophytopsida (or Trimeropsida) is a class (biology), class of early vascular plants from the Devonian, informall ...
s, had independently evolved "megaspory" – their spores were of two distinct sizes, larger
megaspore Megaspores, also called macrospores, are a type of spore that is present in heterosporous plants. These plants have two spore types, megaspores and microspores. Generally speaking, the megaspore, or large spore, germinates into a female gametophy ...
s and smaller microspores. Their reduced gametophytes developed from megaspores retained within the spore-producing organs (megasporangia) of the sporophyte, a condition known as endospory. Seeds consist of an endosporic megasporangium surrounded by one or two sheathing layers (
integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, Exoskeleton, shell, germ or Peel (fruit), rind. Etymology The term is derived from ''integumentum'', which is Latin for "a coverin ...
s). The young sporophyte develops within the seed, which on
germination Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an flowering plant, angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spor ...
splits to release it. The earliest known seed plants date from the latest Devonian
Famennian The Famennian is the latter of two faunal stages in the Late Devonian Epoch. The most recent estimate for its duration estimates that it lasted from around 371.1 million years ago to 359.3 million years ago. An earlier 2012 estimate, still used b ...
stage. Following the evolution of the seed habit, seed plants diversified, giving rise to a number of now-extinct groups, including seed ferns, as well as the modern gymnosperms and angiosperms.
Gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...
s produce "naked seeds" not fully enclosed in an ovary; modern representatives include
conifers Conifers are a group of cone-bearing seed plants, a subset of gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gym ...
,
cycad Cycads are seed plant A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryop ...
s, ''
Ginkgo ''Ginkgo'' is a genus of non-flowering seed plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and is now the only living genus within t ...
'', and
Gnetales Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three Reli ...
.
Angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
produce seeds enclosed in a structure such as a
carpel Gynoecium (; ) is most commonly used as a collective term for the parts of a flower that produce ovules and ultimately develop into the fruit and seeds. The gynoecium is the innermost whorl (botany), whorl of a flower; it consists of (one or m ...
or an
ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the bo ...
. Ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a
sister clade In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...
to the gymnosperms.


Plant physiology

Plant
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying the ...
encompasses all the internal chemical and physical activities of plants associated with life. Chemicals obtained from the air, soil and water form the basis of all
plant metabolism Plant physiology is a subdiscipline of botany concerned with the functioning, or physiology, of plants. Closely related fields include plant morphology (structure of plants), plant ecology (interactions with the environment), phytochemistry (bio ...
. The energy of sunlight, captured by oxygenic photosynthesis and released by
cellular respiration Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive the bulk production of ATP. Cellular respiration may be des ...
, is the basis of almost all life. Photoautotrophs, including all green plants, algae and
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum (biology), phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's ...
gather energy directly from sunlight by photosynthesis.
Heterotroph A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...
s including all animals, all fungi, all completely parasitic plants, and non-photosynthetic bacteria take in organic molecules produced by photoautotrophs and respire them or use them in the construction of cells and tissues.
Respiration Respiration may refer to: Biology * Cellular respiration Cellular respiration is the process by which biological fuels are oxidised in the presence of an inorganic electron acceptor such as oxygen to produce large amounts of energy, to drive ...
is the oxidation of carbon compounds by breaking them down into simpler structures to release the energy they contain, essentially the opposite of photosynthesis. Molecules are moved within plants by transport processes that operate at a variety of spatial scales. Subcellular transport of ions, electrons and molecules such as water and
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
s occurs across
cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the cytoplasm, interior of all Cell (biology), cells from th ...
s. Minerals and water are transported from roots to other parts of the plant in the transpiration stream.
Diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
,
osmosis Osmosis (, ) is the spontaneous net movement or diffusion of solvent molecules through a selectively permeable membrane, selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of ...
, and
active transport In Cellular Biology, cellular biology, ''active transport'' is the movement of molecules or ions across a cell membrane Second law of thermodynamics, from a region of lower concentration to a region of higher concentration—against the concentra ...
and
mass flow Mass flow, also known as mass transfer and bulk flow, is the movement of fluids down a pressure or temperature gradient,Moyes & Schulte (2008). Principles of Animal Physiology. Pearson Benjamin Cummings. San Francisco, California particularly in ...
are all different ways transport can occur. Examples of elements that plants need to transport are
nitrogen Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the pnictogens. It is a common element in the ...
,
phosphorus Phosphorus is a chemical element with the Symbol (chemistry), symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly Reactivity (chemistry), reactive, phosphor ...
,
potassium Potassium is the chemical element with the Symbol (chemistry), symbol K (from New Latin, Neo-Latin ''wikt:kalium#Latin, kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little fo ...
,
calcium Calcium is a chemical element A chemical element is a species of atoms that have a given number of protons in their atomic nucleus, nuclei, including the pure Chemical substance, substance consisting only of that species. Unlike chemica ...
,
magnesium Magnesium is a chemical element with the Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group ...
, and
sulfur Sulfur (or sulphur in British English British English (BrE, en-GB, or BE) is, according to Oxford Dictionaries, " English as used in Great Britain, as distinct from that used elsewhere". More narrowly, it can refer specifically to the ...
. In vascular plants, these elements are extracted from the soil as soluble ions by the roots and transported throughout the plant in the xylem. Most of the elements required for
plant nutrition Plant nutrition is the study of the chemical elements and Chemical compound, compounds necessary for plant growth and reproduction, plant metabolism and their external supply. In its absence the plant is unable to complete a normal life cycle, or ...
come from the chemical breakdown of soil minerals.
Sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refined ...
produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and
plant hormones Plant hormone (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, from embryogenesis, the regulation of Organ (anatomy), ...
are transported by a variety of processes.


Plant hormones

Plants are not passive, but respond to external signals such as light, touch, and injury by moving or growing towards or away from the stimulus, as appropriate. Tangible evidence of touch sensitivity is the almost instantaneous collapse of leaflets of ''
Mimosa pudica ''Mimosa pudica'' (from la, pudica "shy, bashful or shrinking"; also called sensitive plant, sleepy plant, action plant, touch-me-not, shameplant) is a creeping annual or perennial A perennial plant or simply perennial is a plant that li ...
'', the insect traps of
Venus flytrap The Venus flytrap (''Dionaea muscipula'') is a carnivorous plant native to humid subtropical climate, subtropical wetlands on the East Coast of the United States in North Carolina and South Carolina. It catches its prey—chiefly insects and a ...
and
bladderwort ''Utricularia'', commonly and collectively called the bladderworts, is a genus of carnivorous plants consisting of approximately 233 species (precise counts differ based on classification opinions; a 2001 publication lists 215 species).Salmon, Br ...
s, and the pollinia of orchids. The hypothesis that plant growth and development is coordinated by
plant hormone Plant hormone (or phytohormones) are signal molecules, produced within plants, that occur in extremely low concentrations. Plant hormones control all aspects of plant growth and development, from embryogenesis, the regulation of Organ (anatomy), ...
s or plant growth regulators first emerged in the late 19th century. Darwin experimented on the movements of plant shoots and roots towards
light Light or visible light is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequency, fr ...
and
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...
, and concluded "It is hardly an exaggeration to say that the tip of the radicle . . acts like the brain of one of the lower animals . . directing the several movements". About the same time, the role of
auxin Auxins (plural of auxin ) are a class of plant hormones (or plant-growth regulators) with some morphogen-like characteristics. Auxins play a cardinal role in coordination of many growth and behavioral processes in plant life cycles and are essenti ...
s (from the Greek , to grow) in control of plant growth was first outlined by the Dutch scientist Frits Went. The first known auxin,
indole-3-acetic acid Indole-3-acetic acid (IAA, 3-IAA) is the most common naturally occurring plant hormone of the auxin class. It is the best known of the auxins, and has been the subject of extensive studies by plant physiologists. IAA is a derivative of indole, con ...
(IAA), which promotes cell growth, was only isolated from plants about 50 years later. This compound mediates the tropic responses of shoots and roots towards light and gravity. The finding in 1939 that plant
callus A callus is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may o ...
could be maintained in culture containing IAA, followed by the observation in 1947 that it could be induced to form roots and shoots by controlling the concentration of growth hormones were key steps in the development of plant biotechnology and genetic modification.
Cytokinin Cytokinins (CK) are a class of plant hormones that promote cell division, or cytokinesis, in plant roots and shoots. They are involved primarily in Cell (biology), cell growth and cellular differentiation, differentiation, but also affect apical ...
s are a class of plant hormones named for their control of cell division (especially
cytokinesis Cytokinesis () is the part of the cell division biological process, process during which the cytoplasm of a single eukaryotic cell divides into two daughter cells. Cytoplasmic division begins during or after the late stages of Mitosis, nuclear d ...
). The natural cytokinin
zeatin Zeatin is a cytokinin derived from adenine, which occurs in the form of a ''cis''- and a ''trans''-isomer and conjugates. Zeatin was discovered in immature corn kernels from the genus ''Zea (plant), Zea''. It promotes growth of lateral buds and wh ...
was discovered in corn, ''
Zea mays Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American English, North American and Australian English), is a cereal grain first domesticated by indigenous peoples of Mexico, indigenous ...
'', and is a derivative of the
purine Purine is a heterocyclic compound, heterocyclic aromatic organic compound that consists of two rings (pyrimidine and imidazole) fused together. It is water-soluble. Purine also gives its name to the wider class of molecules, purines, which includ ...
adenine Adenine () (nucleoside#List of nucleosides and corresponding nucleobases, symbol A or Ade) is a nucleobase (a purine derivative). It is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. Th ...
. Zeatin is produced in roots and transported to shoots in the xylem where it promotes cell division, bud development, and the greening of chloroplasts. The gibberelins, such as gibberelic acid are
diterpene Diterpenes are a class of chemical compounds composed of four isoprene units, often with the molecular formula C20H32. They are biosynthesized by plants, animals and fungi via the HMG-CoA reductase pathway, with geranylgeranyl pyrophosphate being ...
s synthesised from
acetyl CoA Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining che ...
via the
mevalonate pathway The mevalonate pathway, also known as the isoprenoid pathway or HMG-CoA reductase HMG-CoA reductase (3-hydroxy-3-methyl-glutaryl-coenzyme A reductase, official symbol HMGCR) is the rate-controlling enzyme (NADH-dependent, ; NADPH-dependent, ...
. They are involved in the promotion of germination and dormancy-breaking in seeds, in regulation of plant height by controlling stem elongation and the control of flowering.
Abscisic acid Abscisic acid (ABA) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy Dormancy is a period in an organism, organism's Biological life cycle, life cycle when growth, development, and (in an ...
(ABA) occurs in all land plants except liverworts, and is synthesised from
carotenoid Carotenoids (), also called tetraterpenoids, are yellow, orange, and red organic compound, organic pigments that are produced by plants and algae, as well as several bacteria, and Fungus, fungi. Carotenoids give the characteristic color to pumpki ...
s in the chloroplasts and other plastids. It inhibits cell division, promotes seed maturation, and dormancy, and promotes stomatal closure. It was so named because it was originally thought to control
abscission Abscission () is the shedding of various parts of an organism, such as a plant dropping a leaf, fruit, flower, or seed. In zoology, abscission is the intentional shedding of a body part, such as the shedding of a claw, husk, or the autotomy of a ...
.
Ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon-carbon double ...
is a gaseous hormone that is produced in all higher plant tissues from
methionine Methionine (symbol Met or M) () is an essential amino acid in humans. As the precursor of other amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical rol ...
. It is now known to be the hormone that stimulates or regulates fruit ripening and abscission, and it, or the synthetic growth regulator ethephon which is rapidly metabolised to produce ethylene, are used on industrial scale to promote ripening of cotton,
pineapple The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centurie ...
s and other climacteric crops. Another class of
phytohormone Plant hormone (or phytohormones) are signal molecule In biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For i ...
s is the
jasmonate Jasmonate (JA) and its derivatives are lipid-based plant hormones that regulate a wide range of processes in plants, ranging from growth and photosynthesis to reproductive development. In particular, JAs are critical for plant defense against herbi ...
s, first isolated from the oil of '' Jasminum grandiflorum'' which regulates wound responses in plants by unblocking the expression of genes required in the
systemic acquired resistance Systemic acquired resistance (SAR) is a "whole-plant" resistance response that occurs following an earlier localized exposure to a pathogen. SAR is analogous to the innate immune system found in animals, and although there are many shared aspects be ...
response to pathogen attack. In addition to being the primary energy source for plants, light functions as a signalling device, providing information to the plant, such as how much sunlight the plant receives each day. This can result in adaptive changes in a process known as
photomorphogenesis In developmental biology Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of Regeneration (biology), regeneration, asexual reproduction, metamorphos ...
.
Phytochrome Phytochromes are a class of photoreceptor in plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not ...
s are the photoreceptors in a plant that are sensitive to light.


Plant anatomy and morphology

Plant anatomy Plant anatomy or phytotomy is the general term for the study of the internal Anatomy, structure of plants. Originally it included plant morphology, the description of the physical form and external structure of plants, but since the mid-20th centu ...
is the study of the structure of plant cells and tissues, whereas
plant morphology Phytomorphology is the study of the morphology (biology), physical form and external structure of plants.Raven, P. H., R. F. Evert, & S. E. Eichhorn. ''Biology of Plants'', 7th ed., page 9. (New York: W. H. Freeman, 2005). . This is usually cons ...
is the study of their external form. All plants are multicellular eukaryotes, their DNA stored in nuclei. The characteristic features of
plant cell Plant cells are the cells present in Viridiplantae, green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids ...
s that distinguish them from those of animals and fungi include a primary
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biolog ...
composed of the polysaccharides
cellulose Cellulose is an organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon chemical bond, bonds. Due to carbon's ability to Catenation, catenate (form chains with other ...
,
hemicellulose A hemicellulose (also known as polyose) is one of a number of heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose Cellulose is an organic compound In chemistry, organic compounds are generally any ch ...
and
pectin Pectin ( grc, πηκτικός ': "congealed" and "curdled") is a heteropolysaccharide, a structural acid contained in the primary lamella, in the middle lamella, and in the cell walls of terrestrial plants. The principal, chemical component of ...
, larger
vacuole A vacuole () is a membrane-bound organelle which is present in Plant cell, plant and Fungus, fungal Cell (biology), cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water ...
s than in animal cells and the presence of
plastid The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the cells of plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingd ...
s with unique photosynthetic and biosynthetic functions as in the chloroplasts. Other plastids contain storage products such as starch (
amyloplasts Amyloplasts are a type of plastid The plastid (Greek: πλαστός; plastós: formed, molded – plural plastids) is a membrane-bound organelle found in the cells of plants Plants are predominantly Photosynthesis, photosynthetic eukaryo ...
) or lipids ( elaioplasts). Uniquely,
streptophyte Streptophyta (), informally the streptophytes (, from the Greek language, Greek ''strepto'' 'twisted', for the morphology of the sperm of some members), is a clade of plants. The composition of the clade varies considerably between authors, but ...
cells and those of the green algal order Trentepohliales divide by construction of a phragmoplast as a template for building a
cell plate image:Phragmoplast.png, 300px, Phragmoplast and cell plate formation in a plant cell during cytokinesis. Left side: Phragmoplast forms and cell plate starts to assemble in the center of the cell. Towards the right: Phragmoplast enlarges in a donut ...
late in
cell division Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...
. The bodies of
vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of embryophyte, land plants ( accepted known species) that have lignin, lignified tissue (biology), tissues (the xylem) for conducting water and ...
s including
clubmosses Lycopodiopsida is a class of vascular plants known as lycopods, lycophytes or other terms including the component lyco-. Members of the class are also called clubmosses, firmosses, spikemosses and quillworts. They have dichotomously branching s ...
,
fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The Polypodiophyta, polypodiophytes include all living pteridop ...
s and seed plants (
gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...
s and
angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
) generally have aerial and subterranean subsystems. The
shoot In botany, a plant shoot consists of any plant stem A stem is one of two main structural axes of a vascular plant, the other being the root. It supports leaf, leaves, flowers and fruits, transports water and dissolved substances between the ...
s consist of stems bearing green photosynthesising
leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...
and reproductive structures. The underground vascularised
root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often b ...
s bear root hairs at their tips and generally lack chlorophyll. Non-vascular plants, the
liverworts The Marchantiophyta () are a division of non-vascular plant, non-vascular embryophyte, land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the pla ...
,
hornworts Hornworts are a group of Non-vascular plant, non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, ...
and
mosses Mosses are small, non-vascular flower A flower, sometimes known as a bloom or blossom, is the reproduction, reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to ...
do not produce ground-penetrating vascular roots and most of the plant participates in photosynthesis. The
sporophyte A sporophyte () is the diploid multicellular stage in the biological life cycle, life cycle of a plant or alga which produces asexual Spore, spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyt ...
generation is nonphotosynthetic in liverworts but may be able to contribute part of its energy needs by photosynthesis in mosses and hornworts. The root system and the shoot system are interdependent – the usually nonphotosynthetic root system depends on the shoot system for food, and the usually photosynthetic shoot system depends on water and minerals from the root system. Cells in each system are capable of creating cells of the other and producing
adventitious Important structures in plant development are buds, shoots, roots, leaf, leaves, and flowers; plants produce these tissues and structures throughout their life from meristems located at the tips of organs, or between mature tissues. Thus, a living p ...
shoots or roots.
Stolons In biology, stolons (from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are ...
and
tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing s ...
s are examples of shoots that can grow roots. Roots that spread out close to the surface, such as those of willows, can produce shoots and ultimately new plants. In the event that one of the systems is lost, the other can often regrow it. In fact it is possible to grow an entire plant from a single leaf, as is the case with plants in ''Streptocarpus'' sect. ''Saintpaulia'', or even a single
cell Cell most often refers to: * Cell (biology) The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a Cell membrane, membrane, and contains many biomolecules such as proteins, D ...
– which can dedifferentiate into a
callus A callus is an area of thickened and sometimes hardened skin that forms as a response to repeated friction, pressure, or other irritation. Since repeated contact is required, calluses are most often found on the feet and hands, but they may o ...
(a mass of unspecialised cells) that can grow into a new plant. In vascular plants, the xylem and phloem are the conductive tissues that transport resources between shoots and roots. Roots are often adapted to store food such as sugars or
starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, ...
, as in
sugar beet A sugar beet is a plant whose root contains a high concentration of sucrose and which is grown commercially for sugar production. In plant breeding, it is known as the Altissima cultivar group of the common beet (''Beta vulgaris''). Together wit ...
s and carrots. Stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as
cacti A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...
, food as in potato
tubers Tubers are a type of enlarged structure used as storage organ A storage organ is a part of a plant specifically modified for storage of energy (generally in the form of carbohydrates) or water. Storage organs often grow underground, where they ...
, or reproduce vegetatively as in the
stolons In biology, stolons (from Latin ''wikt:stolo, stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are ...
of
strawberry The garden strawberry (or simply strawberry; ''Fragaria × ananassa'') is a widely grown Hybrid (biology), hybrid species of the genus ''Fragaria'', collectively known as the strawberries, which are cultivated worldwide for their fruit. The f ...
plants or in the process of
layering Layering has evolved as a common means of vegetative propagation of numerous species in natural environments. Layering is also utilized by horticulturists to propagate desirable plants. Natural layering typically occurs when a branch touches ...
. Leaves gather sunlight and carry out
photosynthesis Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemica ...
. Large, flat, flexible, green leaves are called foliage leaves.
Gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, '' Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμν ...
s, such as
conifer Conifers are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single ...
s,
cycad Cycads are seed plant A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryop ...
s, ''
Ginkgo ''Ginkgo'' is a genus of non-flowering seed plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and is now the only living genus within t ...
'', and
gnetophytes Gnetophyta () is a division of plants (alternatively considered the subclass Gnetidae or order Gnetales), grouped within the gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, ...
are seed-producing plants with open seeds.
Angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
are seed-producing plants that produce flowers and have enclosed seeds. Woody plants, such as
azalea Azaleas are flowering shrubs in the genus ''Rhododendron'', particularly the former sections '' Tsutsusi'' (evergreen) and '' Pentanthera'' (deciduous). Azaleas bloom in the spring (April and May in the temperate Northern Hemisphere, and Octo ...
s and
oak An oak is a tree or shrub in the genus ''Quercus'' (; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks. The common name "oak" also appears in the names of species in related genera, notably ''L ...
s, undergo a secondary growth phase resulting in two additional types of tissues: wood (secondary
xylem Xylem is one of the two types of transport tissue in vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of embryophyte, land plants ( accepted known species) that have lignin, ...
) and bark (secondary
phloem Phloem (, ) is the living biological tissue, tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This tran ...
and
cork Cork or CORK may refer to: Materials * Cork (material) Cork is an Permeability (earth sciences), impermeable buoyancy, buoyant material, the Cork cambium, phellem layer of bark (botany), bark tissue that is harvested for commercial use prima ...
). All gymnosperms and many angiosperms are woody plants. Some plants reproduce sexually, some asexually, and some via both means. Although reference to major morphological categories such as root, stem, leaf, and trichome are useful, one has to keep in mind that these categories are linked through intermediate forms so that a continuum between the categories results. Furthermore, structures can be seen as processes, that is, process combinations.


Systematic botany

Systematic botany is part of systematic biology, which is concerned with the range and diversity of organisms and their relationships, particularly as determined by their evolutionary history. It involves, or is related to, biological classification, scientific taxonomy and
phylogenetics In biology, phylogenetics (; from Greek language, Greek wikt:φυλή, φυλή/wikt:φῦλον, φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary his ...
. Biological classification is the method by which botanists group organisms into categories such as
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
or
species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
. Biological classification is a form of scientific taxonomy. Modern taxonomy is rooted in the work of
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement in 1761 as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalise ...
, who grouped species according to shared physical characteristics. These groupings have since been revised to align better with the
Darwinian Darwinism is a scientific theory, theory of Biology, biological evolution developed by the English naturalist Charles Darwin (1809–1882) and others, stating that all species of organisms arise and develop through the natural selection of smal ...
principle of
common descent Common descent is a concept in evolutionary biology applicable when one species is the ancestor of two or more species later in time. All living beings are in fact descendants of a unique ancestor commonly referred to as the last universal comm ...
– grouping organisms by ancestry rather than superficial characteristics. While scientists do not always agree on how to classify organisms,
molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
, which uses DNA sequences as data, has driven many recent revisions along evolutionary lines and is likely to continue to do so. The dominant classification system is called
Linnaean taxonomy Linnaean taxonomy can mean either of two related concepts: # The particular form of Taxonomy (biology), biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the ta ...
. It includes ranks and
binomial nomenclature In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name compos ...
. The nomenclature of botanical organisms is codified in the
International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "trad ...
(ICN) and administered by the
International Botanical Congress International Botanical Congress (IBC) is an international meeting of Botany, botanists in all scientific fields, authorized by the International Association of Botanical and Mycological Societies (IABMS) and held every six years, with the locatio ...
. Kingdom
Plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...
ae belongs to
Domain Domain may refer to: Mathematics *Domain of a function, the set of input values for which the (total) function is defined **Domain of definition of a partial function **Natural domain of a partial function **Domain of holomorphy of a function *Dom ...
Eukaryota Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
and is broken down recursively until each species is separately classified. The order is: Kingdom;
Phylum In biology, a phylum (; plural: phyla) is a level of classification or taxonomic rank below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (biology), division has been used instead of ph ...
(or Division); Class; Order;
Family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
;
Genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
(plural ''genera'');
Species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...
. The scientific name of a plant represents its genus and its species within the genus, resulting in a single worldwide name for each organism. For example, the tiger lily is '' Lilium columbianum''. ''Lilium'' is the genus, and ''columbianum'' the
specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name compos ...
. The combination is the name of the species. When writing the scientific name of an organism, it is proper to capitalise the first letter in the genus and put all of the specific epithet in lowercase. Additionally, the entire term is ordinarily italicised (or underlined when italics are not available). The evolutionary relationships and heredity of a group of organisms is called its
phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among va ...
. Phylogenetic studies attempt to discover phylogenies. The basic approach is to use similarities based on shared inheritance to determine relationships. As an example, species of '' Pereskia'' are trees or bushes with prominent leaves. They do not obviously resemble a typical leafless
cactus A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Greek ...
such as an ''
Echinocactus ''Echinocactus'' is a genus of cactus, cacti in the subfamily Cactoideae. The generic name derives from the Ancient Greek εχινος (''echinos''), meaning "spiny," and ''cactus''. It and ''Ferocactus'' are the two genera of barrel cactus. Me ...
''. However, both ''Pereskia'' and ''Echinocactus'' have spines produced from areoles (highly specialised pad-like structures) suggesting that the two genera are indeed related. Judging relationships based on shared characters requires care, since plants may resemble one another through
convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
in which characters have arisen independently. Some
euphorbia ''Euphorbia'' is a very large and diverse genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In ...
s have leafless, rounded bodies adapted to water conservation similar to those of globular cacti, but characters such as the structure of their flowers make it clear that the two groups are not closely related. The cladistic method takes a systematic approach to characters, distinguishing between those that carry no information about shared evolutionary history – such as those evolved separately in different groups ( homoplasies) or those left over from ancestors ( plesiomorphies) – and derived characters, which have been passed down from innovations in a shared ancestor (
apomorphies In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
). Only derived characters, such as the spine-producing areoles of cacti, provide evidence for descent from a common ancestor. The results of cladistic analyses are expressed as
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not ...
s: tree-like diagrams showing the pattern of evolutionary branching and descent. From the 1990s onwards, the predominant approach to constructing phylogenies for living plants has been
molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...
, which uses molecular characters, particularly DNA sequences, rather than morphological characters like the presence or absence of spines and areoles. The difference is that the genetic code itself is used to decide evolutionary relationships, instead of being used indirectly via the characters it gives rise to. Clive Stace describes this as having "direct access to the genetic basis of evolution." As a simple example, prior to the use of genetic evidence, fungi were thought either to be plants or to be more closely related to plants than animals. Genetic evidence suggests that the true evolutionary relationship of multicelled organisms is as shown in the cladogram below – fungi are more closely related to animals than to plants.
In 1998, the
Angiosperm Phylogeny Group The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botany, botanists who collaborate to establish a consensus on the Taxonomy (biology), taxonomy of flowering plants (angiosperms) that reflects new knowledge abo ...
published a
phylogeny A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree (graph theory), tree showing the evolutionary relationships among va ...
for flowering plants based on an analysis of DNA sequences from most families of flowering plants. As a result of this work, many questions, such as which families represent the earliest branches of
angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek language, Greek words ('container, vessel') and ('seed'), and refers to ...
, have now been answered. Investigating how plant species are related to each other allows botanists to better understand the process of evolution in plants. Despite the study of model plants and increasing use of DNA evidence, there is ongoing work and discussion among taxonomists about how best to classify plants into various
taxa In biology, a taxon (back-formation from ''Taxonomy (biology), taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known ...
. Technological developments such as computers and
electron microscope An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
s have greatly increased the level of detail studied and speed at which data can be analysed.


Symbols

A few symbols are in current use in botany. A number of others are obsolete; for example, Linnaeus used planetary symbols for woody, herbaceous and perennial plants, and Willd used (Saturn) for neuter in addition to (Mercury) for hermaphroditic. The following symbols are still used:Niki Simpson
Botanical symbols: a new symbol set for new images
''Botanical Journal of the Linnean Society'', Volume 162, Issue 2, February 2010, Pages 117–129
:♀ female :♂ male :⚥ hermaphrodite/bisexual :⚲ vegetative (asexual) reproduction :◊ sex unknown :☉ annual : 16px (⚇)
biennial Biennial means (an event) lasting for two years or occurring every two years. The related term biennium is used in reference to a period of two years. In particular, it can refer to: * Biennial plant, a plant which blooms in its second year and th ...
: 16px (♾)
perennial A perennial plant or simply perennial is a plant that lives more than two years. The term (''wikt:per-#Prefix, per-'' + ''wikt:-ennial#Suffix, -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annual pl ...
:☠ poisonous :🛈 further information :× crossbred hybrid :+ grafted hybrid


See also

* Branches of botany * Evolution of plants *
Glossary of botanical terms This glossary of botanical terms is a list of definitions of terms and concepts relevant to botany and plants in general. Terms of plant morphology are included here as well as at the more specific Glossary of plant morphology and Glossary o ...
*
Glossary of plant morphology This page provides a glossary of plant morphology. Botanists and other biologists who study plant morphology use a number of different terms to classify and identify plant organs and parts that can be observed using no more than a handheld magnify ...
* List of botany journals * List of botanists * List of botanical gardens *
List of botanists by author abbreviation __NOTOC__ A * Aa – Hubertus Antonius van der Aa Hubertus or Hubert ( 656 – 30 May 727 A.D.) was a Christian saint who became the first bishop of Liège in 708 A.D. He is the patron saint of hunters, mathematicians, opticians and metal ...
* List of domesticated plants * List of flowers * List of systems of plant taxonomy * Outline of botany * Timeline of British botany


Notes


References


Citations


Sources

* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Supporting Information
* * * * * * * * * * * * * ** * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *


External links

* {{Authority control Articles containing video clips