Plant

Plants Temporal range: Mesoproterozoic–present Pha. Proterozoic Archean Had.
Rhodophyta Fern Spirotaenia
Scientific classification
Domain:	Eukaryota
Clade:	Diaphoretickes
(unranked):	Archaeplastida
Kingdom:	Plantae H.F.Copel., 1956
Superdivisions
see text
Synonyms
Viridiplantae Cavalier-Smith 1981[1] Chlorobionta Jeffrey 1982, emend. Bremer 1985, emend. Lewis and McCourt 2004[2] Chlorobiota Kenrick and Crane 1997[3] Chloroplastida Adl et al., 2005 [4] Phyta Barkley 1939 emend. Holt & Uidica 2007 Cormophyta Endlicher, 1836 Cormobionta Rothmaler, 1948 Euplanta Barkley, 1949 Telomobionta Takhtajan, 1964 Embryobionta Cronquist et al., 1966 Metaphyta Whittaker, 1969

Plants are the

All living things were traditionally placed into one of two groups, plants and

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

Evolution

Diversity

There are about 382,000 accepted

The naming of plants is governed by the International Code of Nomenclature for algae, fungi, and plants^[32] and the International Code of Nomenclature for Cultivated Plants.^[33]

Evolutionary history

The ancestors of land plants evolved in water. An algal scum formed on the land 1,200 million years ago, but it was not until the Ordovician, around 450 million years ago, that the first land plants appeared, with a level of organisation like that of bryophytes.^[34][35] However, fossils of organisms with a flattened thallus in Precambrian rocks suggest that multicellular freshwater eukaryotes existed over 1000 mya.^[36]

Primitive land plants began to diversify in the late Silurian, around 420 million years ago. Bryophytes, club mosses, and ferns then appear in the fossil record.^[37] Early plant anatomy is preserved in cellular detail in an early Devonian fossil assemblage from the Rhynie chert. These early plants were preserved by being petrified in chert formed in silica-rich volcanic hot springs.^[38]

By the end of the Devonian, most of the basic features of plants today were present, including roots, leaves and

• 
  Cross-section of a stem of Rhynia, an early land plant, preserved in Rhynie chert from the early Devonian
• 
  By the Devonian, plants had adapted to land with roots and woody stems.
• 
  In the Carboniferous, horsetails such as Asterophyllites proliferated in swampy forests.
• 
  Conifers became diverse and often dominant in the Jurassic. Cone of Araucaria mirabilis.
• 
  Adaptive radiation in the Cretaceous created many flowering plants, such as Sagaria in the Ranunculaceae.

Phylogeny

In 2019, a

Archaeplastida	Rhodophyta Glaucophyta Viridiplantae Chlorophyta Prasinococcales   Mesostigmatophyceae Chlorokybophyceae Spirotaenia Klebsormidiales Chara Coleochaetales Zygnematophyceae Embryophytes Bryophytes Hornworts Liverworts Mosses Lycophytes Ferns Spermatophytes Gymnosperms Angiosperms (seed plants) (land plants) (green plants)	"chlorophyte algae" "streptophyte algae"

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 vacuole, chloroplasts, and the strong flexible cell wall, which is outside the cell membrane. Chloroplasts are derived from what was once a symbiosis of a non-photosynthetic cell and photosynthetic cyanobacteria. The cell wall, made mostly of cellulose, allows plant cells to swell up with water without bursting. The vacuole allows the cell to change in size while the amount of cytoplasm stays the same.^[54]

Plant structure

Plants photosynthesize, manufacturing food molecules (sugars) using energy obtained from light. Plant cells contain chlorophylls inside their chloroplasts, which are green pigments that are used to capture light energy. The end-to-end chemical equation for photosynthesis is:^[56]

${\displaystyle {\ce {6CO2{}+6H2O{}->[{\text{light}}]C6H12O6{}+6O2{}}}}$

This causes plants to release oxygen into the atmosphere. Green plants provide a substantial proportion of the world's molecular oxygen, alongside the contributions from photosynthetic algae and cyanobacteria.^[57][58][59]

Plants that have secondarily adopted a parasitic lifestyle may lose the genes involved in photosynthesis and the production of chlorophyll.^[60]

Growth and repair

Growth is determined by the interaction of a plant's genome with its physical and biotic environment.^[61] Factors of the physical or abiotic environment include temperature, water, light, carbon dioxide, and nutrients in the soil.^[62] Biotic factors that affect plant growth include crowding, grazing, beneficial symbiotic bacteria and fungi, and attacks by insects or plant diseases.^[63]

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.^[64] 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.^[65]

Reproduction

Plants reproduce to generate offspring, whether sexually, involving gametes, or asexually, involving ordinary growth. Many plants use both mechanisms.^[66]

Sexual

When reproducing sexually, plants have complex lifecycles involving

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 runners enable plants to grow to cover an area, forming a clone. Many plants grow food storage structures such as tubers or bulbs which may each develop into a new plant.^[69]

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.^[70][71]

Disease resistance

Plants use pattern-recognition receptors to recognize pathogens such as bacteria that cause plant diseases. This recognition triggers a protective response. The first such plant receptors were identified in rice^[72] and in Arabidopsis thaliana.^[73]

Genomics

Plants have some of the largest genomes of all organisms.^[74] The largest plant genome (in terms of gene number) is that of wheat (Triticum aestivum), predicted to encode ≈94,000 genes^[75] and thus almost 5 times as many as the human genome. The first plant genome sequenced was that of Arabidopsis thaliana which encodes about 25,500 genes.^[76] 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)^[77] while the largest, from the Norway spruce (Picea abies), extends over 19.6 Gb (encoding about 28,300 genes).^[78]

Ecology

Distribution

Plants are distributed almost worldwide. While they inhabit several biomes which can be divided into a multitude of ecoregions,^[79] only the hardy plants of the Antarctic flora, consisting of algae, mosses, liverworts, lichens, and just two flowering plants, have adapted to the prevailing conditions on that southern continent.^[80]

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 grassland, savanna, and tropical rainforest.^[81]

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%

Numerous animals have coevolved with plants; flowering plants have evolved pollination syndromes, suites of flower traits that favour their reproduction. Many, including insect and bird partners, are pollinators, visiting flowers and accidentally transferring pollen in exchange for food in the form of pollen or nectar.^[84]

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.^[85] Myrmecophytes are plants that have coevolved with ants. The plant provides a home, and sometimes food, for the ants. In exchange, the ants defend the plant from herbivores and sometimes competing plants. Ant wastes serve as organic fertilizer.^[86]

The majority of plant species have fungi associated with their root systems in a mutualistic symbiosis known as mycorrhiza. The fungi help the plants gain water and mineral nutrients from the soil, while the plant gives the fungi carbohydrates manufactured in photosynthesis.^[87] Some plants serve as homes for

Some 1% of plants are parasitic. They range from the semi-parasitic mistletoe that merely takes some nutrients from its host, but still has photosynthetic leaves, to the fully-parasitic broomrape and toothwort 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.^[91]

Plants that grow on other plants, usually trees, without parasitizing them, are called

• 
  Bee gathering pollen (orange pollen basket on its leg)
• 
  Hummingbird visiting a flower for nectar
• 
  Seed dispersal by animals: many hooked Geum urbanum fruits attached to a dog's fur
• 
  Legumes have root nodules containing symbiotic Rhizobium nitrogen fixing bacteria.
• 
  A

  sundew leaf with sticky hairs curling to trap and digest a fly

Competition for shared resources reduces a plant's growth.[95]^[96] Shared resources include sunlight, water and nutrients. Light is a critical resource because it is necessary for photosynthesis.^[95] Plants use their leaves to shade other plants from sunlight and grow quickly to maximize their own expose.^[95] Water too is essential for photosynthesis; roots compete to maximize water uptake from soil.^[97] 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.^[97] Minerals are important for plant growth and development.^[98] Common nutrients competed for amongst plants include nitrogen, phosphorus, and potassium.^[99]

Importance to humans

Food

Human cultivation of plants is the core of

Structural resources and fibres from plants are used to construct dwellings and to manufacture clothing. Wood is used for buildings, boats, and furniture, and for smaller items such as musical instruments and sports equipment. Wood is pulped to make paper and cardboard.^[118] Cloth is often made from cotton, flax, ramie or synthetic fibres such as rayon, derived from plant cellulose. Thread used to sew cloth likewise comes in large part from cotton.^[119]

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 historic gardens, national parks, rainforests, forests with colourful autumn leaves, and festivals such as Japan's^[120] and America's cherry blossom festivals.^[121]

Plants may be grown indoors as

The

Plants including

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.^[136] Plants and especially flowers form the subjects of many paintings.^[137][138]

Negative effects

Weeds are commercially or aesthetically undesirable plants growing in managed environments such as in agriculture and gardens.^[139] People have spread many plants beyond their native ranges; some of these plants have become invasive, damaging existing ecosystems by displacing native species, and sometimes becoming serious weeds of cultivation.^[140]

Some plants that produce

Further reading

General:

• Evans, L.T. (1998). Feeding the Ten Billion – Plants and
  ISBN 0-521-64685-5
  .
• Kenrick, Paul; Crane, Peter R. (1997). The Origin and Early Diversification of Land Plants: A Cladistic Study. Washington, D.C.:
  ISBN 1-56098-730-8
  .
• Raven, Peter H.; Evert, Ray F.; Eichhorn, Susan E. (2005). Biology of Plants (7th ed.). New York:
  ISBN 0-7167-1007-2
  .
• Taylor, Thomas N.; Taylor, Edith L. (1993). The Biology and Evolution of Fossil Plants. Englewood Cliffs, New Jersey:
  ISBN 0-13-651589-4
  .

Species estimates and counts:

• International Union for Conservation of Nature and Natural Resources (IUCN) Species Survival Commission (2004). IUCN Red List The IUCN Red List of Threatened Species.
• Prance, G. T. (2001). "Discovering the Plant World". Taxon. 50 (2, Golden Jubilee Part 4): 345–359.
  JSTOR 1223885
  .

External links

The Wikibook Dichotomous Key has a page on the topic of: Plantae

• Index Nominum Algarum
• Interactive Cronquist classification. Archived 10 February 2006.
• Plant Resources of Tropical Africa. Archived 11 June 2010.
• Tree of Life. Archived 9 March 2022 at the Wayback Machine.

Botanical and vegetation databases

• African Plants Initiative database
• Australia
• Chilean plants at Chilebosque
• e-Floras (Flora of China, Flora of North America and others). Archived 19 February 2022 at the Wayback Machine.
• Flora Europaea
• Flora of Central Europe (in German)
• Flora of North America. Archived 19 February 2022 at the Wayback Machine.
• List of Japanese Wild Plants Online. Archived 16 March 2022 at the Wayback Machine.
• Meet the Plants-National Tropical Botanical Garden. Archived 16 June 2007.
• Lady Bird Johnson Wildflower Center – Native Plant Information Network at University of Texas, Austin
• United States Department of Agriculture not limited to continental US species.