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Plants are the that form the kingdom Plantae; they are predominantly . This means that they obtain their energy from , using derived from with to produce from and water, using the green pigment . Exceptions are that have lost the genes for chlorophyll and photosynthesis, and obtain their energy from other plants or fungi.

Historically, as in Aristotle's biology, the plant kingdom encompassed all living things that were not , and included and . Definitions have narrowed since then; current definitions exclude the fungi and some of the algae. By the definition used in this article, plants form the (green plants), which consists of the and the or land plants (, , , , , and other , and ). A definition based on includes the Viridiplantae, along with the and the , in the clade .

There are about 380,000 known of plants, of which the majority, some 260,000, . They range in size from single cells to the tallest . Green plants provide a substantial proportion of the world's molecular oxygen; the sugars they create supply the energy for most of Earth's and other , including animals, either or rely on organisms which do so.

, , and are basic human foods and have been for millennia. People use plants for many purposes, such as building materials, ornaments, , and, in great variety, . The scientific study of plants is known as , a branch of .


Definition

Taxonomic history
All living things were traditionally placed into one of two groups, plants and . This classification dates from (384–322 BC), who distinguished different levels of beings in his biology,
(2024). 9780226360492, University of Chicago Press. .
based on whether living things had a "sensitive soul" or like plants only a "vegetative soul".
(2024). 9781408836224, Bloomsbury Publishing.
, Aristotle's student, continued his work in plant taxonomy and classification. Much later, (1707–1778) created the basis of the modern system of scientific classification, but retained the animal and plant kingdoms, naming the plant kingdom the Vegetabilia.


Alternative concepts
When the name Plantae or plant is applied to a specific group of organisms or , it usually refers to one of four concepts. From least to most inclusive, these four groupings are:

Land plants, also known as Plantae sensu strictissimoMulticellularPlants in the strictest sense include , , , and , as well as fossil plants similar to these surviving groups (e.g., Metaphyta Whittaker, 1969, Plantae , 1971).
Green plants, also known as , Viridiphyta, Chlorobionta or ChloroplastidaPlantae sensu strictoSome unicellular, some multicellularPlants in a strict sense include the , and land plants that emerged within them, including . The relationships between plant groups are still being worked out, and the names given to them vary considerably. The Viridiplantae encompasses a group of organisms that have in their , possess and and have bound by only two membranes that are capable of photosynthesis and of storing starch. This clade is the main subject of this article (e.g., Plantae , 1956).
, also known as Plastida or PrimoplantaePlantae sensu latoSome unicellular, some multicellularPlants in a broad sense comprise the green plants listed above plus the red algae () and the glaucophyte algae () that store outside the , in the cytoplasm. This clade includes all of the organisms that eons ago acquired their primary chloroplasts directly by engulfing (e.g., Plantae Cavalier-Smith, 1981).
Old definitions of plant (obsolete)Plantae sensu amploSome unicellular, some multicellularPlants in the widest sense included the unrelated groups of , and on older, obsolete classifications (e.g. Plantae or Vegetabilia Linnaeus 1751, Plantae Haeckel 1866, Metaphyta Haeckel, 1894, Plantae Whittaker, 1969).


Evolution

Diversity
There are about 382,000 accepted of plants, of which the great majority, some 283,000, . The table below shows some species count estimates of different green plant (Viridiplantae) divisions. About 85–90% of all plants are flowering plants. Several projects are currently attempting to collect records on all plant species in online databases, e.g. the World Flora Online.

Plants range in scale from single-celled organisms such as (from 10 micrometres across) and (less than 3 micrometres across),

(2024). 9780123858764, .
to the largest trees () such as the conifer Sequoia sempervirens (up to tall ) and the angiosperm Eucalyptus regnans (up to tall ).

+ Diversity of living green plant (Viridiplantae) divisions by number of species
Green algae (chlorophytes)3800–4300
(1995). 9780521304191, Cambridge University Press.
Green algae (e.g. & )2800–6000
(1995). 9780521304191, Cambridge University Press.
Liverworts6000–8000
(2024). 9780521660976, Cambridge University Press.
Hornworts100–200
(1992). 9780914868217, Field Museum of Natural History.
Mosses12000
Clubmosses1200
(2024). 9780716710073, W. H. Freeman and Company. .
Ferns, whisk ferns & horsetails11000

(seed plants)
Cycads160
(1988). 9780716719465, W. H. Freeman and Company.
Ginkgo1
(1993). 9780136515890, .
Conifers630
Gnetophytes70
Flowering plants258650 International Union for Conservation of Nature and Natural Resources, 2006. IUCN Red List of Threatened Species:Summary Statistics

The naming of plants is governed by the International Code of Nomenclature for algae, fungi, and plants and the International Code of Nomenclature for Cultivated Plants.

(2024). 9780521866453, Cambridge University Press. .


Evolutionary history
The ancestors of land plants evolved in water. An algal scum formed on the land , but it was not until the , around , that the first land plants appeared, with a level of organisation like that of bryophytes. However, fossils of organisms with a flattened in rocks suggest that multicellular freshwater eukaryotes existed over 1000 mya.

Primitive land plants began to diversify in the late , around . Bryophytes, club mosses, and ferns then appear in the fossil record.

(2024). 9783319773155, Springer. .
Early plant anatomy is preserved in cellular detail in an early fossil assemblage from the . These early plants were preserved by being petrified in formed in silica-rich volcanic hot springs.

By the end of the Devonian, most of the basic features of plants today were present, including roots, leaves and in trees such as . The Carboniferous Period saw the development of forests in swampy environments dominated by clubmosses and horsetails, including some as large as trees, and the appearance of early , the first . The Permo-Triassic extinction event radically changed the structures of communities. This may have set the scene for the evolution of flowering plants in the (~), with an adaptive radiation in the so rapid that Darwin called it an "abominable mystery". diversified from the Late Triassic onwards, and became a dominant part of floras in the .

File:Rhynia stem.jpg |Cross-section of a stem of , an early land plant, preserved in from the early File:Devonianscene-green.jpg |By the , plants had adapted to land with roots and woody stems. File:Asterophyllites Equisetiformis.jpg |In the , such as Asterophyllites proliferated in swampy forests. File:Petrified Araucaria cone.jpg| became diverse and often dominant in the . Cone of Araucaria mirabilis. File:Sagaria cilentana (cropped).jpg |Adaptive radiation in the created many , such as in the .


Phylogeny
In 2019, a based on and from 1,153 plant species was proposed. The placing of algal groups is supported by phylogenies based on genomes from the Mesostigmatophyceae and Chlorokybophyceae that have since been sequenced. Both the "chlorophyte algae" and the "streptophyte algae" are treated as (vertical bars beside phylogenetic tree diagram) in this analysis, as the land plants arose from within those groups. The classification of Bryophyta is supported both by Puttick et al. 2018, and by phylogenies involving the hornwort genomes that have also since been sequenced.


Physiology

Plant cells
Plant cells have distinctive features that other eukaryotic cells (such as those of animals) lack. These include the large water-filled central , , and the strong flexible , which is outside the . Chloroplasts are of a non-photosynthetic cell and photosynthetic . The cell wall, made mostly of , allows plant cells to without bursting. The vacuole allows the cell to change in size while the amount of stays the same.


Plant structure
Most plants are . Plant cells differentiate into multiple cell types, forming tissues such as the with specialized and of leaf veins and , and organs with different physiological functions such as to absorb water and minerals, stems for support and to transport water and synthesized molecules, for photosynthesis, and for reproduction.


Photosynthesis
Plants , manufacturing food molecules () using energy obtained from . Plant cells contain inside their chloroplasts, which are green pigments that are used to capture light energy. The end-to-end chemical equation for photosynthesis is:

6CO2{} + 6H2O{} ->\text{light} C6H12O6{} + 6O2{}

This causes plants to release into the atmosphere. Green plants provide a substantial proportion of the world's molecular oxygen, alongside the contributions from photosynthetic algae and cyanobacteria.

(2024). 9781317897231, Routledge.

Plants that have secondarily adopted a parasitic lifestyle may lose the genes involved in photosynthesis and the production of chlorophyll.


Growth and repair
Growth is determined by the interaction of a plant's with its physical and biotic environment. Factors of the physical or abiotic environment include , , light, , and in the soil. Biotic factors that affect plant growth include crowding, grazing, beneficial symbiotic bacteria and fungi, and attacks by insects or .

Frost and dehydration can damage or kill plants. Some plants have antifreeze proteins, heat-shock proteins and sugars in their cytoplasm that enable them to tolerate these stresses. Plants are continuously exposed to a range of physical and biotic stresses which cause DNA damage, but they can tolerate and repair much of this damage.


Reproduction
Plants reproduce to generate offspring, whether sexually, involving , or asexually, involving ordinary growth. Many plants use both mechanisms.


Sexual
When reproducing sexually, plants have complex lifecycles involving alternation of generations. One generation, the , which is (with 2 sets of ), gives rise to the next generation, the , which is (with one set of chromosomes). Some plants also reproduce asexually via . In some non-flowering plants such as mosses, the sexual gametophyte forms most of the visible plant. In seed plants (gymnosperms and flowering plants), the sporophyte forms most of the visible plant, and the gametophyte is very small. Flowering plants reproduce sexually using flowers, which contain male and female parts: these may be within the same (hermaphrodite) flower, on , or . The produces male gametes that enter the to fertilize the egg cell of the female gametophyte. Fertilization takes place within the or ovaries, which develop into that contain . Fruits may be dispersed whole, or they may split open and the individually.


Asexual
Plants reproduce asexually by growing any of a wide variety of structures capable of growing into new plants. At the simplest, plants such as mosses or liverworts may be broken into pieces, each of which may regrow into whole plants. The propagation of flowering plants by cuttings is a similar process. Structures such as enable plants to grow to cover an area, forming a . Many plants grow food storage structures such as or which may each develop into a new plant.

Some non-flowering plants, such as many liverworts, mosses and some clubmosses, along with a few flowering plants, grow small clumps of cells called gemmae which can detach and grow.


Disease resistance
Plants use pattern-recognition receptors to recognize such as bacteria that cause plant diseases. This recognition triggers a protective response. The first such plant receptors were identified in and in Arabidopsis thaliana.


Genomics
Plants have some of the largest genomes of all organisms. The largest plant genome (in terms of gene number) is that of ( Triticum aestivum), predicted to encode ≈94,000 genes and thus almost 5 times as many as the . The first plant genome sequenced was that of Arabidopsis thaliana which encodes about 25,500 genes. In terms of sheer DNA sequence, the smallest published genome is that of the carnivorous bladderwort ( Utricularia gibba) at 82 Mb (although it still encodes 28,500 genes) while the largest, from the ( Picea abies), extends over 19.6 Gb (encoding about 28,300 genes).


Ecology

Distribution
Plants are distributed almost worldwide. While they inhabit several which can be divided into a multitude of , only the hardy plants of the , consisting of algae, mosses, liverworts, lichens, and just two flowering plants, have adapted to the prevailing conditions on that southern continent.
(2018). 9783662562314, Springer.

Plants are often the dominant physical and structural component of the habitats where they occur. Many of the Earth's biomes are named for the type of vegetation because plants are the dominant organisms in those biomes, such as , , and tropical rainforest.


Primary producers
The photosynthesis conducted by land plants and algae is the ultimate source of energy and organic material in nearly all ecosystems. Photosynthesis, at first by cyanobacteria and later by photosynthetic eukaryotes, radically changed the composition of the early Earth's anoxic atmosphere, which as a result is now 21% . Animals and most other organisms are , relying on oxygen; those that do not are confined to relatively rare anaerobic environments. Plants are the in most terrestrial ecosystems and form the basis of the in those ecosystems. Plants form about 80% of the world biomass at about of carbon.


Ecological relationships
Numerous animals have coevolved with plants; flowering plants have evolved pollination syndromes, suites of flower traits that favour their reproduction. Many, including and , are , visiting flowers and accidentally transferring pollen in exchange for food in the form of pollen or .

Many animals disperse seeds that are adapted for such dispersal. Various mechanisms of dispersal have evolved. Some fruits offer nutritious outer layers attractive to animals, while the seeds are adapted to survive the passage through the animal's gut; others have hooks that enable them to attach to a mammal's fur.

(2011). 9780199563609, Oxford University Press.
are plants that have coevolved with . The plant provides a home, and sometimes food, for the ants. In exchange, the ants defend the plant from and sometimes competing plants. Ant wastes serve as organic .
(2024). 9781405131148, .

The majority of plant species have fungi associated with their root systems in a mutualistic known as . The fungi help the plants gain water and mineral nutrients from the soil, while the plant gives the fungi carbohydrates manufactured in photosynthesis. Some plants serve as homes for fungi that protect the plant from herbivores by producing toxins. The fungal endophyte Neotyphodium coenophialum in grass has pest status in the American cattle industry.

Many have nitrogen-fixing bacteria in nodules of their roots, which fix nitrogen from the air for the plant to use; in return, the plants supply sugars to the bacteria.

(2024). 9781403475213, Heinemann-Raintree Library. .
Nitrogen fixed in this way can become available to other plants, and is important in agriculture; for example, farmers may grow a of a legume such as beans, followed by a cereal such as wheat, to provide with a reduced input of nitrogen fertilizer.

Some 1% of . They range from the semi-parasitic that merely takes some nutrients from its host, but still has photosynthetic leaves, to the fully-parasitic and that acquire all their nutrients through connections to the roots of other plants, and so have no chlorophyll. Full parasites can be extremely harmful to their plant hosts.

Plants that grow on other plants, usually trees, without parasitizing them, are called . These may support diverse arboreal ecosystems. Some may indirectly harm their host plant, such as by intercepting light. like the begin as epiphytes, but eventually set their own roots and overpower and kill their host. Many , , ferns, and mosses grow as epiphytes.

(2024). 9783319818474, .
Among the epiphytes, the bromeliads accumulate water in their leaf axils; these can support complex aquatic food webs.

Some 630 species of plants are carnivorous, such as the ( Dionaea muscipula) and ( Drosera species). They trap small animals and digest them to obtain mineral nutrients, especially and .

(2024). 9780198833727, Oxford University Press.

File:Honey Bee gathering pollen image by Dr. Raju Kasambe DSCN4801 (13) (cropped).jpg|Bee gathering (orange on its leg) File:Purple-throated carib hummingbird feeding (cropped).jpg| visiting a flower for File:Epizoochory - dog with hooked Geum fruits in his fur (detail).jpg| by animals: many hooked fruits attached to a dog's fur File:Robinia pseudoacacia root nodules.JPG| have containing symbiotic nitrogen fixing bacteria. File:Drosera capensis bend.JPG|A leaf with sticky hairs curling to trap and digest a fly


Competition
Competition for shared resources reduces a plant's growth.
(2024). 9780199830060 .
(2015). 9789401790130
Shared resources include sunlight, water and nutrients. Light is a critical resource because it is necessary for photosynthesis. Plants use their leaves to shade other plants from sunlight and grow quickly to maximize their own expose. Water too is essential for photosynthesis; roots compete to maximize water uptake from soil. Some plants have deep roots that are able to locate water stored deep underground, and others have shallower roots that are capable of extending longer distances to collect recent rainwater. Minerals are important for plant growth and development. Common nutrients competed for amongst plants include nitrogen, phosphorus, and potassium.


Importance to humans

Food
Human cultivation of plants is the core of , which in turn has played a key role in the history of world civilizations.
(2013). 9780313396328, ABC-CLIO. .
Humans depend on plants for , either directly or as feed in . Agriculture includes for arable crops, for vegetables and fruit, and for timber. About 7,000 species of plant have been used for food, though most of today's food is derived from only 30 species. The major include such as rice and wheat, starchy roots and tubers such as and , and legumes such as and . such as and provide , while fruit and contribute and minerals to the diet. , , and are major crops whose -containing products serve as mild stimulants. The study of plant uses by people is called economic botany or .
(2016). 9781316675397, Cambridge University Press.


Medicines
are a primary source of , both for their medicinal and physiological effects, and for the industrial synthesis of a vast array of organic chemicals. The details of each plant and the chemicals it yields are described in the linked subpages. Many hundreds of medicines, as well as , are derived from plants, both traditional medicines used in and chemical substances purified from plants or first identified in them, sometimes by ethnobotanical search, and then synthesised for use in modern medicine. Modern medicines derived from plants include , , , , , , and . Plants used in herbalism include , , , and Saint John's wort. The of , De materia medica, describing some 600 medicinal plants, was written between 50 and 70 CE and remained in use in Europe and the Middle East until around 1600 CE; it was the precursor of all modern pharmacopoeias.
(2024). 9780199873982, Oxford University Press. .
(2024). 9781848580398, Arcturus Publishing. .


Nonfood products
Plants grown as industrial crops are the source of a wide range of products used in manufacturing. Nonfood products include , , pigments, , , , alkaloids, and . Products derived from plants include soaps, shampoos, perfumes, cosmetics, paint, varnish, turpentine, rubber, , lubricants, linoleum, plastics, inks, and gums. Renewable fuels from plants include , and other .
(2024). 9781493914470, Springer. .
The , and are derived from the remains of aquatic organisms including in . Many of the coal fields date to the period of Earth's history. Terrestrial plants also form , a source of natural gas.
(2024). 9780495383376, Cengage Learning. .
(2024). 9780128003749, . .

Structural resources and fibres from plants are used to construct dwellings and to manufacture clothing. is used for buildings, boats, and furniture, and for smaller items such as musical instruments and sports equipment. Wood is pulped to make and .

(2024). 9783527309979, Wiley-VCH.
Cloth is often made from , , or synthetic fibres such as , derived from plant cellulose. Thread used to sew cloth likewise comes in large part from cotton.


Ornamental plants
Thousands of plant species are cultivated for their beauty and to provide shade, modify temperatures, reduce wind, abate noise, provide privacy, and reduce soil erosion. Plants are the basis of a multibillion-dollar per year tourism industry, which includes travel to , , , with colourful autumn leaves, and festivals such as
(1996). 9780804820561, Tuttle. .
and America's cherry blossom festivals.

Plants may be grown indoors as , or in specialized buildings such as . Plants such as Venus flytrap, and resurrection plant are sold as novelties. Art forms specializing in the arrangement of cut or living plant include , , and the arrangement of cut or dried flowers. have sometimes changed the course of history, as in .


In science
The traditional study of plants is the science of . Basic biological research has often used plants as its . In , the breeding of pea plants allowed to derive the basic laws governing inheritance, and examination of chromosomes in maize allowed Barbara McClintock to demonstrate their connection to inherited traits. The plant Arabidopsis thaliana is used in laboratories as a model organism to understand how control the growth and development of plant structures. provide a method of dating in , and a record of . The study of plant fossils, or , provides information about the evolutions of plants, reconstructions, and past climate change. Plant fossils can also help determine the age of rocks.
(2024). 9781108483445, Cambridge University Press. .


In mythology, religion, and culture
Plants including trees appear in mythology, religion, and literature. In multiple Indo-European, Siberian, and Native American religions, the motif is depicted as a colossal tree growing on the earth, supporting the heavens, and with its roots reaching into the . It may also appear as a cosmic tree or an eagle and serpent tree. Forms of the world tree include the archetypal tree of life, which is in turn connected to the Eurasian concept of the .
(2024). 9783727816024, Saint-Paul.
Another widespread ancient motif, found for example in Iran, has a tree of life flanked by a pair of confronted animals.

Flowers are often used as memorials, gifts and to mark special occasions such as births, deaths, weddings and holidays. Flower arrangements may be used to send hidden messages.

(2024). 9781623496449, Texas A&M University Press.
Plants and especially flowers form the subjects of many paintings.


Negative effects
are commercially or aesthetically undesirable plants growing in managed environments such as in agriculture and gardens. People have spread many plants beyond their native ranges; some of these plants have become , damaging existing ecosystems by displacing native species, and sometimes becoming serious weeds of cultivation.

Some plants that produce , including grasses, invoke in people who suffer from . Many plants produce toxins to protect themselves from herbivores. Major classes of plant toxins include , , and . These can be harmful to humans and livestock by ingestion

(2009). 9781909686229, Windgather Press. .
9781601076748, UCANR Publications. .
or, as with , by contact.
(2004). 9780190288709, Oxford University Press. .
Some plants have negative effects on other plants, preventing seedling growth or the growth of nearby plants by releasing chemicals.
(2016). 9789386102041, Scientific Publishers. .


See also


Further reading
General:
  • Evans, L.T. (1998). Feeding the Ten Billion – Plants and Growth. Cambridge University Press..
  • Kenrick, Paul; Crane, Peter R. (1997). The Origin and Early Diversification of Land Plants: A Cladistic Study. Washington, D.C.: Smithsonian Institution Press. .
  • Raven, Peter H.; Evert, Ray F.; Eichhorn, Susan E. (2005). Biology of Plants (7th ed.). New York: W.H. Freeman and Company. .
  • Taylor, Thomas N.; Taylor, Edith L. (1993). The Biology and Evolution of Fossil Plants. Englewood Cliffs, New Jersey: . .

Species estimates and counts:


External links
  • Index Nominum Algarum
  • Https://florabase.calm.wa.gov.au/phylogeny/cronq88.html" target="_blank" rel="nofollow"> Interactive Cronquist classification. Archived 10 February 2006.
  • Https://www.prota.org/uk/about+prota/" target="_blank" rel="nofollow"> Plant Resources of Tropical Africa. Archived 11 June 2010.
  • Tree of Life. .

Botanical and vegetation databases

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