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Botany, also called , plant biology or phytology, is the
science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is something that is truth, true. The usual test for a statement of ...

science
of
plant Plants are predominantly photosynthetic 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 ...

plant
life and a branch of
biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanisms, Development ...

biology
. A botanist, plant scientist or phytologist is a
scientist A scientist is a person who conducts scientific research The scientific method is an Empirical evidence, empirical method of acquiring knowledge that has characterized the development of science since at least the 17th century. It involves ...

scientist
who specialises in this field. The term "botany" comes from the
Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the diale ...
word (''botanē'') meaning "
pasture Pasture (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Rom ...

pasture
", "
herbs In general use, herbs are a widely distributed and widespread group of plants, excluding vegetables Vegetables are parts of plants that are consumed by humans or other animals as food. The original meaning is still commonly used and is appl ...

herbs
" "
grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...
", or "
fodder Fodder (), also called provender (), is any agricultural Agriculture is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise ...

fodder
"; is in turn derived from (), "to feed" or "to
graze
graze
". Traditionally, botany has also included the study of
fungi A fungus (plural The plural (sometimes abbreviated An abbreviation (from Latin ''brevis'', meaning ''short'') is a shortened form of a word or phrase, by any method. It may consist of a group of letters, or words taken from the full ...

fungi
and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
by
mycologists Mycology is the branch of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, p ...
and
phycologists Phycology (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...
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 botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist ...
. Nowadays, botanists (in the strict sense) study approximately 410,000
species In biology, a species is the basic unit of biological classification, 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 individu ...

species
of
land plants The Embryophyta (), or land plants, are the most familiar group of green plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into ...

land plants
of which some 391,000 species are
vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windpipe' + φυτά ''phutá'' 'plants'), form a large group of plants ( 300,000 ...
s (including approximately 369,000 species of
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s), and approximately 20,000 are
bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of the four basic operations of arithmetic, the ways that numbers are combined to make new n ...

bryophyte
s. Botany originated in prehistory as
herbalism Herbal medicine (also herbalism) is the study of pharmacognosy Pharmacognosy is the study of plants and other natural substances as possible sources of drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a mi ...
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 File:Petersfield Physic Garden - geograph.org.uk - 17502.jpg, upPetersfield 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 med ...
s, often attached to
monasteries A monastery is a building or complex of buildings comprising the domestic quarters and workplaces of monastics, monk A monk (, from el, μοναχός, ''monachos'', "single, solitary" via Latin Latin (, or , ) is a classical langua ...

monasteries
, 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. is ...

botanical garden
s attached to
universities A university () is an of (or ) and which awards s in several . Universities typically offer both and programs in different schools or faculties of learning. The word ''university'' is derived from the ''universitas magistrorum et scholari ...

universities
, 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 plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert lig ...
, and led in 1753 to the
binomial system of 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 composed ...
of
Carl Linnaeus 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 nob ...

Carl Linnaeus
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 the ...
and
live cell imaging Live cell imaging is the study of living cells using time-lapse microscopy. It is used by scientists to obtain a better understanding of biological function through the study of cellular dynamics. Live cell imaging was pioneered in first decade ...
,
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 hig ...

electron microscopy
, 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 (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s and other
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...

protein
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 Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...
and
proteomics Proteomics is the large-scale study of protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Co ...

proteomics
and
DNA sequences A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides Nucleotides are organic molecules , CH4; is among the simplest organic compounds. In chemistry, ...
to classify plants more accurately. Modern botany is a broad, multidisciplinary subject with inputs 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 A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A ...

structure
, growth and differentiation,
reproduction Reproduction (or procreation or breeding) is the biological process Biological processes are those processes that are vital for an organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is ...
,
biochemistry Biochemistry or biological chemistry, is the study of chemical process In a scientific Science () is a systematic enterprise that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and pr ...
and
primary metabolism
primary metabolism
,
chemical products Products are the species formed from chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter In classical physics and genera ...
,
development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking#Development, Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material i ...

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 due to any immediate external injury. Diseases are often known to be medical ...
,
evolutionary relationships
evolutionary relationships
,
systematics Biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), o ...
, and
plant taxonomy Plant taxonomy is the science that finds, identifies, describes, classifies, and names plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert lig ...
. 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 Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
, which study the mechanisms and control of gene expression during differentiation of
plant cell Plant cells are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are class ...

plant cell
s and tissues. Botanical research has diverse applications in providing
staple foods A staple food, food staple, or simply a staple, is a food Food is any substance consumed to provide Nutrient, nutritional support for an organism. Food is usually of plant, animal or Fungus, fungal origin, and contains essential nutrients, ...
, materials such as
timber Lumber, also known as timber, is wood Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, sup ...
,
oil An oil is any nonpolar In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound ...

oil
, rubber,
fibre Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including ...

fibre
and drugs, in modern
horticulture Horticulture is the art of cultivating plants in gardens to produce food and medicinal ingredients, or for comfort and ornamental purposes. Horticulturists are agriculturists who grow flowers, fruits and nuts, vegetables and herbs, as well as or ...
,
agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...

agriculture
and
forestry Forestry is the science and craft of creating, managing, planting, using, conserving and repairing forest A forest is an area of land dominated by tree In botany, a tree is a perennial plant with an elongated Plant stem, ste ...
,
plant propagation Plant propagation is the process by which new plants grow from a variety of sources: seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bro ...
,
breeding Breeding is sexual reproduction Sexual reproduction is a type of reproduction Reproduction (or procreation or breeding) is the biological process by which new individual organism In biology, an organism (from Ancient Greek, Greek: ...
and
genetic modification Genetic engineering, also called genetic modification or genetic manipulation, is the direct manipulation of an organism's gene In biology, a gene (from ''genos'' "...Wilhelm Johannsen coined the word gene to describe the Mendelian_in ...
, 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 An organization, or organisation (English in the Commonwealth of Nations, Commonwealth English; American and Briti ...
, and the maintenance of
biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic, species, and ecosystem level. Terrestrial biodiversity is usually greater near ...

biodiversity
.


History


Early botany

There is evidence humans used plants as far back as 10,000 years ago in the Little Tennessee River Valley, generally as firewood or food. Botany originated as
herbalism Herbal medicine (also herbalism) is the study of pharmacognosy Pharmacognosy is the study of plants and other natural substances as possible sources of drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a mi ...
, 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  A civilization (or civilisation) is a that is characterized by , , a form of government, and systems of communication (such as ). Civilizations are intimately associated with additional char ...

Ancient Egypt
,Manniche, Lisa; An Ancient Egyptian Herbal; American University in Cairo Press; Cairo; 2006; in archaic
Avestan Avestan , also known historically as Zend, comprises two languages: Old Avestan (spoken in the 2nd millennium BCE) and Younger Avestan (spoken in the 1st millennium BCE). The languages are known only from their use as the language of Zoroastrian ...
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 civilization belonging to a period of History of Greece, Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of Classical Antiquity, antiquity ( AD 600). This era wa ...
specifically to
Theophrastus Theophrastus (; grc-gre, Θεόφραστος ; c. 371c. 287 BC), a Greek native of Eresos Eresos (; el, Ερεσός; grc, Ἔρεσος) and its twin beach village Skala Eresou are located in the southwest part of the Greek island of Le ...

Theophrastus
(c. 371–287 BCE), a student of
Aristotle Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questio ...

Aristotle
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 scientist A scientist is a person who conducts scientific research The scientific method is an Empirical evidence, empirical method of acquiring knowledge that has characterize ...
as the "Father of Botany". His major works, ''
Enquiry into Plants Theophrastus's ''Enquiry into Plants'' or ''Historia Plantarum'' ( grc-gre, Περὶ φυτῶν ἱστορία, ''Peri phyton historia'') was, along with his mentor Aristotle's ''History of Animals'', Pliny the Elder's ''Natural History (Pliny) ...
'' and ''On the Causes of Plants'', constitute the most important contributions to botanical science until the
Middle Ages In the history of Europe The history of Europe concerns itself with the discovery and collection, the study, organization and presentation and the interpretation of past events and affairs of the people of Europe since the beginning of ...
, almost seventeen centuries later. Another work from Ancient Greece that made an early impact on botany is ''De Materia Medica'', a five-volume encyclopedia about
herbal medicine Herbal medicine (also herbalism) is the study of pharmacognosy Pharmacognosy is the study of plants and other natural substances as possible sources of drug Uncoated tablets, consisting of about 90% acetylsalicylic acid, along with a mi ...
written in the middle of the first century by Greek physician and pharmacologist
Pedanius Dioscorides Pedanius Dioscorides ( grc-gre, Πεδάνιος Διοσκουρίδης, ; 40–90 AD) was a Greek physician, pharmacologist, botanist, and author of ''De materia medica (Latin Latin (, or , ) is a classical language belonging to th ...
. ''De Materia Medica'' was widely read for more than 1,500 years. Important contributions from the medieval Muslim world include
Ibn Wahshiyya Ibn Waḥshiyyah (Arabic: ; full name Abū Bakr Aḥmad ibn ʿAlī Ibn Waḥshiyyah, Arabic: ), died c. 930, was a Nabataeans of Iraq, Nabataean agriculturalist, toxicologist, and alchemist born in Qussīn, near Kufa in Iraq. He is the author of the ...
's '' Nabatean Agriculture'',
Abū Ḥanīfa Dīnawarī Abū Ḥanīfah Aḥmad ibn Dāwūd Dīnawarī (815–896 CE, Kurdish: Dînewerî; fa, ابوحنيفه دينوری) was an Iranian Iranian may refer to: * Iran Iran ( fa, ایران ), also called Persia and officially the Islami ...
'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, and
Ibn al-Baitar Ḍiyāʾ Al-Dīn Abū Muḥammad ʿAbdllāh Ibn Aḥmad al-Mālaqī, commonly known as Ibn al-Bayṭār () (1197–1248 AD) was an Al-Andalus, Andalusian Arabs, Arab physician, botanist, pharmacist and scientist. His main contribution was to syst ...

Ibn al-Baitar
(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. is ...

botanical garden
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 The University of Oxford Botanic Garden is the oldest botanic garden in Great Britain and one of the oldest scientific gardens in the world. The garden was founded in 1621 as a physic garden upPetersfield Physic Garden A physic garden is a ty ...

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, was a German physician and botanist. His chief notability is as the author of a large book about plants and their uses as medicines, a herbal A herbal is a ...

Leonhart Fuchs
(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. Carl von Linné listed him among the ''"Fathers of Botany"''. Life After studying theology and philoso ...

Otto Brunfels
(1489–1534) and physician
Hieronymus Bock Hieronymus Bock ( Latinised Hieronymus Tragus; c. 1498 – 21 February 1554) was a German botanist Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a ...

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 Valerius Cordus (18 February 1515 – 25 September 1544) was a German physician A physician (American English), medical practitioner (English in the Commonwealth of Nations, Commonwealth English), medical doctor, or simply doctor, is a profe ...

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'', literally, "drug-making"), in its modern technical sense, is a book containing directions for the identification of compound medicine Medicine is t ...
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 botanist with a large herbal garden in London. His 1,484-page illustrated ''Herball, or Generall Historie of Plantes'', first published in 1597, became the most prevalent botany boo ...
(1545–c. 1611) published herbals covering the medicinal uses of plants. Naturalist
Ulisse Aldrovandi Ulisse Aldrovandi (11 September 1522 – 4 May 1605) was an Italy, Italian natural history, naturalist, the moving force behind Orto Botanico dell'Università di Bologna, Bologna's botanical garden, one of the first in Europe. Carl Linnaeus and th ...
(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 prob ...

Polymath
Robert Hooke Robert Hooke FRS FRS may also refer to: Government and politics * Facility Registry System, a centrally managed Environmental Protection Agency database that identifies places of environmental interest in the United States * Family Resources ...
discovered
cells Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Closed spaces * Monastic cell, a small room, hut, or cave in which a monk or religious recluse lives * Prison cell, a room used to hold peopl ...
, a term he coined, in
cork Cork or CORK may refer to: Materials * Cork (material), an impermeable buoyant plant product ** Cork (plug), a cylindrical or conical object used to seal a container ***Wine cork Places Ireland * Cork (city) ** Metropolitan Cork, also known as G ...
, 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 Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, ch ...
were developed comparable to
dichotomous keysIn 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 in ...
, where unidentified plants are placed into
taxon In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechani ...
omic groups (e.g. family, genus and species) by making a series of choices between pairs of
characters Character(s) may refer to: Arts, entertainment, and media Literature * Character (novel), ''Character'' (novel), a 1936 Dutch novel by Ferdinand Bordewijk * Characters (Theophrastus), ''Characters'' (Theophrastus), a classical Greek set of char ...
. 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 Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactions, Physiology, physiological mechanism ...
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 nob ...

Carl von Linné
(Carl Linnaeus) published his
Species Plantarum ' (Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with" ...
, 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 /ˈdʒiː.nəs/ (plural genera /ˈdʒen.ər.ə/) is a taxonomic rank In biological classification In biology, taxonomy () is the scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying gr ...
and the second identified the
species In biology, a species is the basic unit of biological classification, 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 individu ...

species
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 structure A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or ...
,
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), study of the shape of astronomical objects such as nebulae, galaxies ...

morphology
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 JussieuDe Jussieu, the name of a French people, French family which came into prominence towards the close of the sixteenth century, and was known for a century and a half for the botanists it produced. The following are its more eminent members: *Antoine ...

de Jussieu
(1789), and Augustin Pyramus de Candolle, 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, which was influential until the mid-19th century, was influenced by Candolle's approach. Charles Darwin, Darwin's publication of the ''On the Origin of Species, Origin of Species'' 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 Jakob Schleiden, Matthias Schleiden'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 with Theodor Schwann and Rudolf Virchow and was among the first to grasp the significance of the cell nucleus that had been described by Robert Brown (botanist, born 1773), Robert Brown in 1831. In 1855, Adolf Fick formulated Fick's laws of diffusion, Fick's laws that enabled the calculation of the rates of molecular diffusion in biological systems.


Late modern botany

Building upon the gene-chromosome theory of heredity that originated with Gregor Mendel (1822–1884), August Weismann (1834–1914) proved that inheritance only takes place through gametes. 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 was pioneered in the late 19th century by botanists such as Eugenius Warming, who produced the hypothesis that plants form plant community, communities, and his mentor and successor Christen C. Raunkiær whose system for describing Raunkiær plant life-form, plant life forms is still in use today. The concept that the composition of plant communities such as Temperate broadleaf and mixed forests, temperate broadleaf forest changes by a process of ecological succession was developed by Henry Chandler Cowles, Arthur Tansley and Frederic Clements. 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 ecosystems to biology. Building on the extensive earlier work of Alphonse Pyramus de Candolle, Alphonse de Candolle, Nikolai Ivanovich Vavilov, Nikolai Vavilov (1887–1943) produced accounts of the biogeography, Center of origin, 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 physiology, plant physiological processes such as transpiration (the transport of water within plant tissues), the temperature dependence of rates of water evaporation from the leaf surface and the molecular diffusion 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 have enabled precise description of the rates of gas exchange between plants and the atmosphere. Innovations in Statistics, statistical analysis by Ronald Fisher, Frank Yates and others at Rothamsted Research#Statistical science, Rothamsted Experimental Station facilitated rational experimental design and data analysis in botanical research. The discovery and identification of the auxin Plant physiology#Plant hormones, plant hormones by Kenneth V. Thimann in 1948 enabled regulation of plant growth by externally applied chemicals. Frederick Campion Steward pioneered techniques of micropropagation and plant tissue culture 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 chemistry, organic chemical analysis, such as spectroscopy, chromatography and electrophoresis. With the rise of the related molecular-scale biological approaches of molecular biology,
genomics Genomics is an interdisciplinary field of biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interact ...
,
proteomics Proteomics is the large-scale study of protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Co ...

proteomics
and metabolomics, the relationship between the plant genome 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 Cell potency#Totipotency, totipotent and can be grown ''in vitro'' ultimately enabled the use of genetic engineering experimentally to knock out a gene or genes responsible for a specific trait, or to add genes such as Green fluorescent protein, GFP that reporter gene, report when a gene of interest is being expressed. These technologies enable the biotechnological use of whole plants or plant cell cultures grown in bioreactors to synthesise Bt corn, pesticides, Biopharmaceutics, antibiotics or other pharming (genetics), pharmaceuticals, as well as the practical application of genetically modified crops 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. Furthermore, it emphasises structural dynamics. Modern systematics aims to reflect and discover Phylogenetic nomenclature, phylogenetic relationships between plants. Modern Molecular phylogenetics largely ignores morphological characters, relying on DNA sequences as data. Molecular analysis of nucleic acid sequence, DNA sequences from most families of flowering plants enabled the Angiosperm Phylogeny Group to publish in 1998 a phylogenetics, phylogeny of flowering plants, answering many of the questions about relationships among angiosperm families and species. The theoretical possibility of a practical method for identification of plant species and commercial varieties by DNA barcoding 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 and food that provide humans and other organisms with cellular respiration, aerobic respiration with the chemical energy they need to exist. Plants,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
and cyanobacteria are the major groups of organisms that carry out photosynthesis, a process that uses the energy of sunlight to convert water and carbon dioxide 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 into the atmosphere, a gas that is required by anaerobic organism, nearly all living things to carry out cellular respiration. In addition, they are influential in the global carbon cycle, carbon and water cycle, water cycles and plant roots bind and stabilise soils, preventing soil erosion. 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 organelles, cells, tissues, whole plants, plant populations and plant communities. At each of these levels, a botanist may be concerned with the classification (Taxonomy (biology), taxonomy), phylogeny and evolution, structure (Plant anatomy, anatomy and Plant morphology, morphology), or function (Plant physiology, physiology) of plant life. The strictest definition of "plant" includes only the "land plants" or embryophytes, which include seed plants (gymnosperms, including the Pinophyta, pines, and
flowering plant Flowering plants include multiple members of the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greec ...

flowering plant
s) and the free-sporing cryptogams including ferns, Lycopodiopsida, clubmosses, Marchantiophyta, liverworts, hornworts and mosses. Embryophytes are multicellular eukaryotes descended from an ancestor that obtained its energy from sunlight by photosynthesis. They have life cycles with alternation of generations, alternating haploid and diploid phases. The sexual haploid phase of embryophytes, known as the gametophyte, nurtures the developing diploid embryo sporophyte 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), fungi (mycology) – including lichen-forming fungi (lichenology), non-Chlorophyta, chlorophyte
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
(phycology), and viruses (virology). However, attention is still given to these groups by botanists, and fungi (including lichens) and photosynthetic protists are usually covered in introductory botany courses. Paleobotany, Palaeobotanists study ancient plants in the fossil record to provide information about the evolutionary history of plants. Cyanobacteria, 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 chloroplasts in plant cells. The new photosynthetic plants (along with their algal relatives) accelerated the rise in atmospheric oxygen started by the cyanobacteria, great oxygenation event, changing the ancient oxygen-free, Redox, 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, Conservation (ethic), conservation, food security, human food security, introduced species, biologically invasive organisms, carbon sequestration, climate change, and sustainability.


Human nutrition

Virtually all staple foods come either directly from primary production by plants, or indirectly from animals that eat them. Plants and other photosynthetic organisms are at the base of most food chains 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 modern forms of the major staple foods, such as hemp, teff, maize, rice, wheat and other cereal grasses, Pulse (legume), pulses, bananas and plantains, as well as hemp, flax and cotton grown for their fibres, are the outcome of prehistoric selection over thousands of years from among Neolithic founder crops, wild ancestral plants with the most desirable characteristics. Botanists study how plants produce food and how to increase yields, for example through plant breeding, making their work important to humanity's ability to feed the world and provide food security for future generations. Botanists also study weeds, which are a considerable problem in agriculture, and the biology and control of Plant pathology, plant pathogens in agriculture and natural ecosystems. Ethnobotany 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 paleoethnobotany, palaeoethnobotany. Some of the earliest plant-people relationships arose between the Indigenous peoples of the Americas, indigenous 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 and crassulacean acid metabolism. Others make specialised materials like the cellulose and lignin used to build their bodies, and Secondary metabolism, secondary products like resins and aroma compounds.
Plants make various photosynthetic pigments, some of which can be seen here through paper chromatography
Xanthophylls, Xanthophylls
Chlorophyll a, Chlorophyll ''a''
Chlorophyll b, 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 photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
" have unique organelles known as chloroplasts. Chloroplasts are thought to be descended from cyanobacteria that formed endosymbiotic relationships with ancient plant and algal ancestors. Chloroplasts and cyanobacteria contain the blue-green pigment chlorophyll a, chlorophyll ''a''. Chlorophyll ''a'' (as well as its plant and green algal-specific cousin chlorophyll b, chlorophyll ''b'') absorbs light in the blue-violet and orange/red parts of the visible spectrum, spectrum 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 Carbon fixation#Oxygenic photosynthesis, oxygenic photosynthesis, a process that generates molecular oxygen (O2) as a by-product. The light energy captured by chlorophyll a, chlorophyll ''a'' is initially in the form of electrons (and later a proton gradient) that's used to make molecules of Adenosine triphosphate, ATP and NADPH which temporarily store and transport energy. Their energy is used in the light-independent reactions of the Calvin cycle by the enzyme rubisco to produce molecules of the 3-carbon sugar glyceraldehyde 3-phosphate (G3P). Glyceraldehyde 3-phosphate is the first product of photosynthesis and the raw material from which glucose 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, a polymer of fructose is used for the same purpose in the sunflower family Asteraceae. Some of the glucose is converted to sucrose (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 chloroplasts, including synthesising all their fatty acids, and most amino acids. The fatty acids that chloroplasts make are used for many things, such as providing material to build cell membranes out of and making the polymer cutin which is found in the plant cuticle that protects land plants from drying out. Plants synthesise a number of unique polymers like the polysaccharide molecules cellulose, pectin and xyloglucan from which the land plant cell wall is constructed. Vascular land plants make lignin, a polymer used to strengthen the secondary cell walls of xylem tracheids and Xylem vessel element, 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 Ground tissue#Sclerenchyma, sclerenchyma fibres that provide structural support for a plant and is a major constituent of wood. Sporopollenin 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 period. The concentration of carbon dioxide in the atmosphere today is much lower than it was when plants emerged onto land during the Ordovician and Silurian periods. Many monocots like maize and the pineapple and some dicots like the Asteraceae have since independently evolved pathways like Crassulacean acid metabolism and the C4 carbon fixation, carbon fixation pathway for photosynthesis which avoid the losses resulting from photorespiration in the more common C3 carbon fixation, 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. Some of these compounds are toxins such as the alkaloid coniine from conium, hemlock. Others, such as the essential oils Peppermint#Peppermint oil, peppermint oil and lemon oil are useful for their aroma, as flavourings and spices (e.g., capsaicin), and in medicine as pharmaceuticals as in opium from Papaver somniferum, opium poppies. Many medication, medicinal and recreational drugs, such as tetrahydrocannabinol (active ingredient in Cannabis (drug), cannabis), caffeine, morphine and nicotine come directly from plants. Others are simple Derivative (chemistry), derivatives of botanical natural products. For example, the pain killer aspirin is the acetyl ester of salicylic acid, originally isolated from the bark (biology), bark of willow trees, and a wide range of opiate analgesics, painkillers like diamorphine, heroin are obtained by chemical modification of morphine obtained from the opium poppy. Popular stimulants come from plants, such as caffeine from coffee, tea and chocolate, and nicotine from tobacco. Most alcoholic beverages come from fermentation (food), fermentation of carbohydrate-rich plant products such as barley (beer), rice (sake) and grapes (wine). Native Americans in the United States, 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 Ethnobotany, enthnobotanists and then in turn has been used by Pharmaceutical industry, pharmaceutical companies as a way of drug discovery. Plants can synthesise useful coloured dyes and pigments such as the anthocyanins responsible for the red colour of red wine, yellow Reseda luteola, weld and blue Isatis tinctoria, woad used together to produce Lincoln green, indoxyl, source of the blue dye indigo traditionally used to dye denim and the artist's pigments gamboge and rose madder. Sugar, starch, cotton, linen, hemp, some types of rope, wood and particle boards, papyrus and paper, vegetable oils, epicuticular wax, wax, and natural rubber are examples of commercially important materials made from plant tissues or their secondary products. Charcoal, a pure form of carbon made by pyrolysis of wood, has a long charcoal#History, history as a metal-smelting fuel, as a filter material and activated carbon#Applications, adsorbent and as an artist's material and is one of the three ingredients of gunpowder. Cellulose, the world's most abundant organic polymer, can be converted into energy, fuels, materials and chemical feedstock. cellulose#products, Products made from cellulose include rayon and cellophane, methyl cellulose, wallpaper paste, Butanol fuel#Using Alternate Carbon Sources, biobutanol and nitrocellulose, gun cotton. Sugarcane, rapeseed and soy are some of the plants with a highly fermentable sugar or oil content that are used as sources of biofuels, important alternatives to fossil fuels, such as biodiesel. Sweetgrass was used by Native Americans to ward off bugs like mosquitoes. These bug repelling properties of sweetgrass were later found by the American Chemical Society in the molecules phytol and coumarin.


Plant ecology

Plant ecology is the science of the functional relationships between plants and their habitats – the environments where they complete their Biological life cycle, life cycles. Plant ecologists study the composition of local and regional floras, their
biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity is a measure of variation at the Genetics, genetic, species, and ecosystem level. Terrestrial biodiversity is usually greater near ...

biodiversity
, genetic diversity and Fitness (biology), fitness, the adaptation of plants to their environment, and their competitive or mutualism (biology), mutualistic interactions with other species. Some ecologists even rely on Empirical evidence, empirical data 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 (soil) and climatic factors in their environment but can modify these factors too. For example, they can change their environment's albedo, increase Surface runoff, runoff interception, stabilise mineral soils and develop their organic content, and affect local temperature. Plants compete with other organisms in their ecosystem for resources. They interact with their neighbours at a variety of spatial scales in groups, populations and Community (ecology), communities that collectively constitute vegetation. Regions with characteristic Holdridge life zones, vegetation types and dominant plants as well as similar Abiotic component, abiotic and Biotic components, biotic factors, climate, and geography make up biomes like tundra or tropical rainforest. Herbivores eat plants, but plants can plant defence against herbivory, defend themselves and some species are parasitic plant, parasitic or even carnivorous plant, carnivorous. Other organisms form mutualism (biology), mutually beneficial relationships with plants. For example, mycorrhizal fungi and rhizobia provide plants with nutrients in exchange for food, ants are recruited by myrmecophyte, ant plants to provide protection, honey bees, bats and other animals pollinate flowers and seed dispersal#Dispersal by humans, humans and seed dispersal#Dispersal by animals, other animals act as dispersal vectors to spread spores and seeds.


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 can be a useful proxy (climate), proxy for temperature in historical climatology, and the biological effects of climate change, impact of climate change and global warming. Palynology, the analysis of fossil pollen deposits in sediments from geologic timescale, thousands or millions of years ago allows the reconstruction of past climates. Estimates of atmospheric concentrations since the Palaeozoic have been obtained from stomatal densities and the leaf shapes and sizes of ancient land plants. Ozone depletion can expose plants to higher levels of Ultraviolet, ultraviolet radiation-B (UV-B), resulting in lower growth rates. Moreover, information from studies of community (ecology), community ecology, plant
systematics Biological Biology is the natural science Natural science is a branch of science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), o ...
, and taxonomy (biology), taxonomy is essential to understanding climate change#Vegetation, vegetation change, habitat destruction and endangered species, species extinction.


Genetics

Inheritance in plants follows the same fundamental principles of genetics as in other multicellular organisms. Gregor Mendel discovered the Mendelian inheritance, genetic laws of inheritance by studying inherited traits such as shape in ''Pisum sativum'' (peas). What Mendel learned from studying plants has had far-reaching benefits outside of botany. Similarly, "transposon, jumping genes" were discovered by Barbara McClintock 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 hybrid (biology), hybrids are often possible. A familiar example is peppermint, ''Mentha'' × ''piperita'', a Sterility (physiology), sterile hybrid between ''Mentha aquatica'' and spearmint, ''Mentha spicata''. The many cultivated varieties of wheat are the result of multiple inter- and intra-species, specific crosses between wild species and their hybrids. Angiosperms with monoecious flowers often have Self-incompatibility in plants, self-incompatibility mechanisms that operate between the pollen and stigma (botany), stigma so that the pollen either fails to reach the stigma or fails to germinate and produce male gametes. This is one of several methods used by plants to promote plant reproductive morphology, outcrossing. In many land plants the male and female gametes are produced by separate individuals. These species are said to be Plant reproductive morphology#Terminology, dioecious when referring to vascular plant sporophytes and monoecious, dioicous when referring to
bryophyte Bryophytes are an informal group consisting of three divisions Division or divider may refer to: Mathematics *Division (mathematics) Division is one of the four basic operations of arithmetic, the ways that numbers are combined to make new n ...

bryophyte
gametophytes. Unlike in higher animals, where parthenogenesis is rare, asexual reproduction may occur in plants by several different mechanisms. The formation of stem tubers in potato is one example. Particularly in arctic or alpine climate, alpine habitats, where opportunities for fertilisation of flowers zoophily, by animals are rare, plantlets or bulbs, may develop instead of flowers, replacing sexual reproduction with asexual reproduction and giving rise to cloning, clonal populations genetically identical to the parent. This is one of several types of apomixis that occur in plants. Apomixis can also happen in a seed, 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 may occur due to errors in cytokinesis. 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 hybridization event, 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 from the parent species but live within the same geographical area, may be sufficiently successful to form a new sympatric speciation, species. Some otherwise sterile plant polyploids can still reproduce vegetative propagation, vegetatively or by seed apomixis, forming clonal populations of identical individuals. Durum wheat is a fertile tetraploid allopolyploid, while common wheat, bread wheat is a fertile hexaploid. The commercial banana is an example of a sterile, seedless triploid hybrid. Taraxacum officinale, Common dandelion is a triploid that produces viable seeds by apomictic seed. As in other eukaryotes, the inheritance of endosymbiotic organelles like mitochondria and chloroplasts in plants is non-Mendelian. 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 organism#Plants, model plants such as the Thale cress, ''Arabidopsis thaliana'', a weedy species in the mustard family (Brassicaceae). The genome or hereditary information contained in the genes of this species is encoded by about 135 million base pairs of DNA, forming one of the smallest genomes among flowering plants. ''Arabidopsis'' was the first plant to have its genome sequenced, in 2000. The sequencing of some other relatively small genomes, of rice (''Oryza sativa'') and ''Brachypodium distachyon'', has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. Model organism#Plants, Model plants such as ''Arabidopsis thaliana'' are used for studying the molecular biology of
plant cell Plant cells are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are class ...

plant cell
s and the chloroplast. 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 and phloem loading of sugar in C4 plants, plants. The single celled green alga ''Chlamydomonas reinhardtii'', while not an embryophyte itself, contains a chlorophyll b, green-pigmented Chloroplast#Chloroplastida (green algae and plants), chloroplast related to that of land plants, making it useful for study. A red alga ''Cyanidioschyzon merolae'' has also been used to study some basic chloroplast functions. Spinach, peas, soybeans and a moss ''Physcomitrella patens'' are commonly used to study plant cell biology. ''Agrobacterium tumefaciens'', a soil rhizosphere bacterium, can attach to plant cells and infect them with a Callus (cell biology), callus-inducing Ti plasmid by horizontal gene transfer, 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 responsible for nitrogen fixation in the root nodules of Fabaceae, legumes and other plant species. Today, genetic modification of the Ti plasmid is one of the main techniques for introduction of transgenes to plants and the creation of genetically modified crops.


Epigenetics

Epigenetics is the study of heritable changes in gene expression, gene function that cannot be explained by changes in the underlying DNA sequence 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 which determines whether they will be expressed or not. Gene expression can also be controlled by repressor proteins that attach to silencer (DNA), 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 divisions for the remainder of the cell's life. Some epigenetic changes have been shown to be Heritability, heritable, while others are reset in the germ cells. Epigenetic changes in Eukaryote, eukaryotic biology serve to regulate the process of cellular differentiation. During morphogenesis, totipotent stem cells become the various pluripotent cell lines of the embryo, which in turn become fully differentiated cells. A single fertilised egg cell, the zygote, gives rise to the many different
plant cell Plant cells are eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are class ...

plant cell
types including parenchyma, vessel element, xylem vessel elements, phloem sieve tubes, guard cells of the epidermis (botany), epidermis, etc. as it continues to mitosis, divide. The process results from the epigenetic activation of some genes and inhibition of others. Unlike animals, many plant cells, particularly those of the ground tissue#Parenchyma, parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. Exceptions include highly lignified cells, the ground tissue#Sclerenchyma, sclerenchyma 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 remodeling, 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 chloroplasts of plants have a number of biochemical, structural and genetic similarities to cyanobacteria, (commonly but incorrectly known as "blue-green algae") and are thought to be derived from an ancient endosymbiotic theory, endosymbiotic relationship between an ancestral eukaryote, eukaryotic cell and a Chloroplast#Cyanobacterial ancestor, cyanobacterial resident. The
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
are a Polyphyly, polyphyletic 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, sister to the green algal division Chlorophyta, is considered to contain the ancestor of true plants. The Charophyte class Charophyceae and the land plant sub-kingdom Embryophyta together form the monophyletic group or clade Streptophytina. Nonvascular land plants are embryophytes that lack the vascular tissues xylem and phloem. They include mosses, Marchantiophyta, liverworts and hornworts. Pteridophyte, 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 and early Devonian. Representatives of the lycopods have survived to the present day. By the end of the Devonian period, several groups, including the Lycopodiophyta, lycopods, Sphenophyllales, sphenophylls and progymnosperms, had independently evolved "megaspory" – their spores were of two distinct sizes, larger megaspores and smaller microspores. Their reduced gametophytes developed from megaspores retained within the sporangium, 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 (integuments). The young sporophyte develops within the seed, which on germination splits to release it. The earliest known seed plants date from the latest Devonian Famennian stage. Following the evolution of the seed habit, Spermatophyte, seed plants diversified, giving rise to a number of now-extinct groups, including Pteridospermatophyta, seed ferns, as well as the modern gymnosperms and angiosperms. Gymnosperms produce "naked seeds" not fully enclosed in an ovary; modern representatives include Pinophyta, conifers, cycads, ''Ginkgo'', and Gnetophyta, Gnetales. Angiosperms produce seeds enclosed in a structure such as a Gynoecium, carpel or an ovary. Ongoing research on the molecular phylogenetics of living plants appears to show that the angiosperms are a sister clade to the gymnosperms.


Plant physiology

Plant physiology 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 metabolism, plant metabolism. The energy of sunlight, captured by oxygenic photosynthesis and released by cellular respiration, is the basis of almost all life. Phototroph, Photoautotrophs, including all green plants, algae and cyanobacteria gather energy directly from sunlight by photosynthesis. Heterotrophs 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. Cellular respiration, Respiration 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 (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s occurs across cell membranes. Minerals and water are transported from roots to other parts of the plant in the transpiration stream. Diffusion, osmosis, and active transport and mass flow are all different ways transport can occur. Examples of plant nutrition, elements that plants need to transport are nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. 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 come from the chemical breakdown of soil minerals. Sucrose produced by photosynthesis is transported from the leaves to other parts of the plant in the phloem and Plant physiology#Plant hormones, plant hormones are transported by a variety of processes.


Plant hormones

Plants are not passive, but respond to signal transduction, 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'', the insect traps of Venus flytrap and bladderworts, and the pollinia of orchids. The hypothesis that plant growth and development is coordinated by plant hormones or plant growth regulators first emerged in the late 19th century. Darwin experimented on the movements of plant shoots and roots towards heliotropism, light and geotropism, gravity, 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 auxins (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 (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 (cell biology), callus 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. Cytokinins are a class of plant hormones named for their control of cell division (especially cytokinesis). The natural cytokinin zeatin was discovered in corn, ''Zea mays'', and is a derivative of the purine adenine. 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 diterpenes synthesised from Acetyl-CoA carboxylase, acetyl CoA via the mevalonate pathway. 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 (ABA) occurs in all land plants except liverworts, and is synthesised from carotenoids 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. Ethylene#Ethylene as a plant hormone, Ethylene is a gaseous hormone that is produced in all higher plant tissues from methionine. 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, pineapples and other climacteric (botany), climacteric crops. Another class of phytohormones is the jasmonates, 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 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. Phytochromes are the Photoreceptor protein, photoreceptors in a plant that are sensitive to light.


Plant anatomy and morphology

Plant anatomy is the study of the structure of plant cells and tissues, whereas plant morphology 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 eukaryotic Eukaryotes () are organism In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are class ...

plant cell
s that distinguish them from those of animals and fungi include a primary cell wall composed of the polysaccharides cellulose, hemicellulose and pectin, larger vacuoles than in animal cells and the presence of plastids with unique photosynthetic and biosynthetic functions as in the chloroplasts. Other plastids contain storage products such as starch (amyloplasts) or lipids (elaioplasts). Uniquely, streptophyte cells and those of the green algal order Trentepohliales divide by construction of a phragmoplast as a template for building a cell plate late in cell division. The bodies of
vascular plant Vascular plants (from Latin ''vasculum'': duct), also known as Tracheophyta (the tracheophytes , from Greek τραχεῖα ἀρτηρία ''trācheia artēria'' 'windpipe' + φυτά ''phutá'' 'plants'), form a large group of plants ( 300,000 ...
s including Lycopodiopsida, clubmosses, ferns and spermatophyte, seed plants (gymnosperms and angiosperms) generally have aerial and subterranean subsystems. The shoots consist of Plant stem, stems bearing green photosynthesising Leaf, leaves and reproductive structures. The underground vascularised roots bear root hairs at their tips and generally lack chlorophyll. Non-vascular plants, the Marchantiophyta, liverworts, hornworts and mosses do not produce ground-penetrating vascular roots and most of the plant participates in photosynthesis. The sporophyte 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 shoots or roots. Stolons and tubers 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, ''Streptocarpus'' sect. ''Saintpaulia'', or even a single Cell (biology), cell – which can dedifferentiate into a Callus (cell biology), callus (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, as in sugar beets and carrots. Stems mainly provide support to the leaves and reproductive structures, but can store water in succulent plants such as Cactus, cacti, food as in potato tubers, or vegetative reproduction, reproduce vegetatively as in the stolons of strawberry#Cultivation, strawberry plants or in the process of layering. Leaves gather sunlight and carry out photosynthesis. Large, flat, flexible, green leaves are called foliage leaves. Gymnosperms, such as conifers, cycads, ''Ginkgo'', and gnetophyta, gnetophytes are seed-producing plants with open seeds. Angiosperms are Spermatophyte, seed-producing plants that produce flowers and have enclosed seeds. Woody plants, such as azaleas and oaks, undergo a secondary growth phase resulting in two additional types of tissues: wood (secondary xylem) and bark (secondary phloem and Cork cambium, cork). 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. Biological classification is the method by which botanists group organisms into categories such as genus, genera or
species In biology, a species is the basic unit of biological classification, 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 individu ...

species
. Biological classification is a form of Taxonomy (biology), scientific taxonomy. Modern taxonomy is rooted in the work of
Carl Linnaeus 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 nob ...

Carl Linnaeus
, who grouped species according to shared physical characteristics. These groupings have since been revised to align better with the Charles Darwin, Darwinian principle of common descent – grouping organisms by ancestry rather than phenotype, superficial characteristics. While scientists do not always agree on how to classify organisms, molecular phylogenetics, which uses
DNA sequences A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides Nucleotides are organic molecules , CH4; is among the simplest organic compounds. In chemistry, ...
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. It includes ranks and binomial nomenclature. The nomenclature of botanical organisms is codified in the International Code of Nomenclature for algae, fungi, and plants (ICN) and administered by the
International Botanical Congress International Botanical Congress (IBC) is an international meeting of botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist ...
. Kingdom (biology), Kingdom Plantae belongs to Domain (biology), Domain Eukarya and is broken down recursively until each species is separately classified. The order is: Kingdom (biology), Kingdom; Phylum (or Division); Class (biology), Class; Order (biology), Order; Family (biology), Family; Genus (plural ''genera''); Species. 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 Botanical name#Binary name, specific epithet. 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 Phylogenetics, phylogeny. 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 such as an ''Echinocactus''. 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 in which characters have arisen independently. Some euphorbias 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 Cladistics, 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). 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 cladograms: 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, 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 A. Stace, 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 published a phylogenetics, phylogeny 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, 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 Taxon, taxa. Technological developments such as computers and electron microscopes have greatly increased the level of detail studied and speed at which data can be analysed.


See also

* Branches of botany * Evolution of plants * Glossary of botanical terms * Glossary of plant morphology * List of botany journals * List of botanists * List of botanical gardens * List of botanists by author abbreviation * List of domesticated plants * List of flowers * List of systems of plant taxonomy * Outline of botany * Timeline of British botany


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