Plant taxonomy
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Plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
taxonomy is the science that finds, identifies, describes, classifies, and names
plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
s. It is one of the main branches of
taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...
(the science that finds, describes, classifies, and names living things). Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two. In practice, "plant systematics" involves relationships between plants and their
evolution Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
, especially at the higher levels, whereas "plant taxonomy" deals with the actual handling of plant specimens. The precise relationship between taxonomy and systematics, however, has changed along with the goals and methods employed. Plant taxonomy is well known for being turbulent, and traditionally not having any close agreement on circumscription and placement of taxa. See the list of systems of plant taxonomy.


Background

Classification systems serve the purpose of grouping organisms by characteristics common to each group. Plants are distinguished from animals by various traits: they have cell walls made of
cellulose Cellulose is an organic compound with the chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...
, polyploidy, and they exhibit sedentary growth. Where animals have to eat organic molecules, plants are able to change energy from light into organic energy by the process of
photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...
. The basic unit of classification is
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, a group able to breed amongst themselves and bearing mutual resemblance, a broader classification is the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
. Several genera make up a family, and several families an order.


History of classification

The botanical term angiosperm, or flowering plant, comes from the Greek (; 'bottle, vessel') and (; 'seed'); in 1690, the term Angiospermae was coined by Paul Hermann, albeit in reference to only a small subset of the species that are known as angiosperms, today. Hermann's Angiospermae included only flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, which were flowering plants with achenial or schizo-carpic fruits (the whole fruit, or each of its pieces, being here regarded as a seed and naked). The terms Angiospermae and Gymnospermae were used by
Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
in the same sense, albeit with restricted application, in the names of the orders of his class Didynamia. The terms angiosperms and gymnosperm fundamentally changed meaning in 1827, when Robert Brown determined the existence of truly-naked ovules in the Cycadeae and Coniferae. The term ''gymnosperm'' was, from then-on, applied to seed plants with naked ovules, and the term ''angiosperm'' to seed plants with enclosed ovules. However, for many years after Brown's discovery, the primary division of the seed plants was seen as between monocots and dicots, with gymnosperms as a small subset of the dicots. In 1851, Hofmeister discovered the changes occurring in the embryo-sac of flowering plants, and determined the correct relationships of these to the Cryptogamia. This fixed the position of Gymnosperms as a class distinct from Dicotyledons, and the term Angiosperm then, gradually, came to be accepted as the suitable designation for the whole of the flowering plants (other than Gymnosperms), including the classes of Dicotyledons and Monocotyledons. This is the sense in which the term is used, today. In most taxonomies, the flowering plants are treated as a coherent group; the most popular descriptive name has been Angiospermae, with Anthophyta () a second choice (both unranked). The Wettstein system and Engler system treated them as a subdivision (Angiospermae). The Reveal system also treated them as a subdivision (Magnoliophytina), but later split it to Magnoliopsida, Liliopsida, and Rosopsida. The
Takhtajan system A list of systems of plant taxonomy, system of plant taxonomy, the Takhtajan system of plant classification was published by Armen Takhtajan, in several versions from the 1950s onwards. It is usually compared to the Cronquist system. It admits Para ...
and Cronquist system treat them as a division (Magnoliophyta). The Dahlgren system and Thorne system (1992) treat them as a class (Magnoliopsida). The APG system of 1998, and the later 2003 and 2009 revisions, treat the flowering plants as an unranked clade without a formal Latin name (angiosperms). A formal classification was published alongside the 2009 revision in which the flowering plants rank as a subclass (Magnoliidae). The internal classification of this group has undergone considerable revision. The Cronquist system, proposed by Arthur Cronquist in 1968 and published in its full form in 1981, is still widely used but is no longer believed to accurately reflect
phylogeny A phylogenetic tree or phylogeny is a graphical representation which shows the evolutionary history between a set of species or Taxon, taxa during a specific time.Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, M ...
. A consensus about how the flowering plants should be arranged has recently begun to emerge through the work of the Angiosperm Phylogeny Group (APG), which published an influential reclassification of the angiosperms in 1998. Updates incorporating more recent research were published as the APG II system in 2003, the APG III system in 2009, and the APG IV system in 2016. Traditionally, the flowering plants are divided into two groups, * Dicotyledoneae or Magnoliopsida * Monocotyledoneae or Liliopsida to which the Cronquist system ascribes the classes Magnoliopsida (from " Magnoliaceae") and Liliopsida (from " Liliaceae"). Other descriptive names allowed by Article 16 of the ICBN include Dicotyledones or Dicotyledoneae, and Monocotyledones or Monocotyledoneae, which have a long history of use. In plain English, their members may be called "dicotyledons" ("dicots") and "monocotyledons" ("monocots"). The Latin behind these names refers the observation that the dicots most often have two cotyledons, or embryonic leaves, within each seed. The monocots usually have only one, but the rule is not absolute either way. From a broad diagnostic point of view, the number of cotyledons is neither a particularly handy, nor a reliable character. Recent studies, as per the APG, show that the monocots form a
monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...
group (a
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
), but that the dicots are
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
; nevertheless, the majority of dicot species fall into a clade with the eudicots (or tricolpates), with most of the remaining going into another major clade with the magnoliids (containing about 9,000 species). The remainder includes a paraphyletic grouping of early-branching taxa known collectively as the basal angiosperms, plus the families Ceratophyllaceae and Chloranthaceae.


''Plantae'', the Plant Kingdom

The plant kingdom is traditionally divided according to the following:


Identification, classification and description of plants

Three goals of plant taxonomy are the identification, classification and description of plants. The distinction between these three goals is important and often overlooked. Plant identification is a determination of the identity of an unknown plant by comparison with previously collected specimens or with the aid of books or identification manuals. The process of identification connects the specimen with a published name. Once a plant specimen has been identified, its name and properties are known. Plant classification is the placing of known plants into groups or categories to show some relationship. Scientific classification follows a system of rules that standardizes the results, and groups successive categories into a
hierarchy A hierarchy (from Ancient Greek, Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or "at the same level as" one another. Hierarchy ...
. For example, the family to which the lilies belong is classified as follows: * Kingdom:
Plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they are predominantly Photosynthesis, photosynthetic. This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with c ...
ae * Division: Magnoliophyta * Class: Liliopsida * Order:
Liliales Liliales is an order (biology), order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web List of systems of plant classification, system, within the lilioid monocots. This order of necessity includ ...
* Family: Liliaceae The classification of plants results in an organized system for the naming and cataloging of future specimens, and ideally reflects scientific ideas about inter-relationships between plants. The set of rules and recommendations for formal botanical nomenclature, including plants, is governed by the
International Code of Nomenclature for algae, fungi, and plants The ''International Code of Nomenclature for algae, fungi, and plants'' (ICN or ICNafp) 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 tho ...
abbreviated as ICN. Plant description is a formal description of a newly discovered
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, and takes place only after significant scientific work to determine that a species is in fact new to science. New descriptions are usually published in the form of a scientific paper using ICN guidelines. The names of these plants can then be registered to the
International Plant Names Index The International Plant Names Index (IPNI) describes itself as "a database of the names and associated basic bibliographical details of seed plants, ferns and lycophytes." Coverage of plant names is best at the rank of species and genus. It inclu ...
along with other validly published names.


Classification systems

These include; * APG system (''angiosperm phylogeny group'') ** APG II system (''angiosperm phylogeny group II'') ** APG III system (''angiosperm phylogeny group III'') ** APG IV system (''angiosperm phylogeny group IV'') * Bessey system (''a system of plant taxonomy'') * Cronquist system (''taxonomic classification of flowering plants'') * Melchior system


Online databases

*
Plants of the World Online Plants of the World Online (POWO) is an online taxonomic database published by the Royal Botanic Gardens, Kew. History Following the Convention on Biological Diversity, the Royal Botanic Gardens in Kew launched Plants of the World Online i ...
(POWO) *
World Flora Online World Flora Online is an Internet-based compendium of the world's plant species. Description The World Flora Online (WFO) is an open-access database, launched in October 2012 as a follow-up project to The Plant List, with the aim of publishi ...
(WFO) * Ecocrop * EPPO Code * GRIN See Online botany databases


See also

* American Society of Plant Taxonomists * Biophysical environment *
Botanical nomenclature Botanical nomenclature is the formal, scientific naming of plants. It is related to, but distinct from taxonomy (biology), taxonomy. Plant taxonomy is concerned with grouping and classifying plants; Botany, botanical nomenclature then provides na ...
* Citrus taxonomy *
Environmental protection Environmental protection, or environment protection, refers to the taking of measures to protecting the natural environment, prevent pollution and maintain ecological balance. Action may be taken by individuals, advocacy groups and governments. ...
* Herbarium * History of plant systematics * International Association for Plant Taxonomy * Taxonomy of cultivated plants


References


Sources

* * * *


External links


Plant systematics

Tracking Plant Taxonomy Updates discussion group
on
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