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For other uses, see Plant (disambiguation). Plant_sentence_0

For an explanation of similar terms, see Viridiplantae and Green algae. Plant_sentence_1



Temporal range: Mesoproterozoic–present





Scientific classification PlantaePlant_header_cell_0_1_0
Domain:Plant_cell_0_2_0 EukaryotaPlant_cell_0_2_1
(unranked):Plant_cell_0_3_0 DiaphoretickesPlant_cell_0_3_1
(unranked):Plant_cell_0_4_0 ArchaeplastidaPlant_cell_0_4_1
Kingdom:Plant_cell_0_5_0 Plantae

sensu Copeland, 1956Plant_cell_0_5_1


Plants are mainly multicellular organisms, predominantly photosynthetic eukaryotes of the kingdom Plantae. Plant_sentence_2

Historically, plants were treated as one of two kingdoms including all living things that were not animals, and all algae and fungi were treated as plants. Plant_sentence_3

However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria). Plant_sentence_4

By one definition, plants form the clade Viridiplantae (Latin name for "green plants"), a group that includes the flowering plants, conifers and other gymnosperms, ferns and their allies, hornworts, liverworts, mosses, and the green algae, but excludes the red and brown algae. Plant_sentence_5

Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria. Plant_sentence_6

Their chloroplasts contain chlorophylls a and b, which gives them their green color. Plant_sentence_7

Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize, but still have flowers, fruits, and seeds. Plant_sentence_8

Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is also common. Plant_sentence_9

There are about 320,000 species of plants, of which the great majority, some 260–290 thousand, produce seeds. Plant_sentence_10

Green plants provide a substantial proportion of the world's molecular oxygen, and are the basis of most of Earth's ecosystems. Plant_sentence_11

Plants that produce grain, fruit, and vegetables also form basic human foods and have been domesticated for millennia. Plant_sentence_12

Plants have many cultural and other uses, as ornaments, building materials, writing material and, in great variety, they have been the source of medicines and psychoactive drugs. Plant_sentence_13

The scientific study of plants is known as botany, a branch of biology. Plant_sentence_14

Definition Plant_section_0

All living things were traditionally placed into one of two groups, plants and animals. Plant_sentence_15

This classification may date from Aristotle (384 BC – 322 BC), who made the distinction between plants, which generally do not move, and animals, which often are mobile to catch their food. Plant_sentence_16

Much later, when Linnaeus (1707–1778) created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia (later Metaphyta or Plantae) and Animalia (also called Metazoa). Plant_sentence_17

Since then, it has become clear that the plant kingdom as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. Plant_sentence_18

However, these organisms are still often considered plants, particularly in popular contexts. Plant_sentence_19

The term "plant" generally implies the possession of the following traits: multicellularity, possession of cell walls containing cellulose, and the ability to carry out photosynthesis with primary chloroplasts. Plant_sentence_20

Current definitions of Plantae Plant_section_1

When the name Plantae or plant is applied to a specific group of organisms or taxon, it usually refers to one of four concepts. Plant_sentence_21

From least to most inclusive, these four groupings are: Plant_sentence_22


Name(s)Plant_header_cell_1_0_0 ScopePlant_header_cell_1_0_1 DescriptionPlant_header_cell_1_0_2
Land plants, also known as EmbryophytaPlant_cell_1_1_0 Plantae sensu strictissimoPlant_cell_1_1_1 Plants in the strictest sense include the liverworts, hornworts, mosses, and vascular plants, as well as fossil plants similar to these surviving groups (e.g., Metaphyta Whittaker, 1969, Plantae Margulis, 1971).Plant_cell_1_1_2
Green plants, also known as Viridiplantae, Viridiphyta, Chlorobionta or ChloroplastidaPlant_cell_1_2_0 Plantae sensu strictoPlant_cell_1_2_1 Plants in a strict sense include the green algae, and land plants that emerged within them, including stoneworts. The relationships between plant groups are still being worked out, and the names given to them vary considerably. The clade Viridiplantae encompasses a group of organisms that have cellulose in their cell walls, possess chlorophylls a and b and have plastids 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 Copeland, 1956).Plant_cell_1_2_2
Archaeplastida, also known as Plastida or PrimoplantaePlant_cell_1_3_0 Plantae sensu latoPlant_cell_1_3_1 Plants in a broad sense comprise the green plants listed above plus the red algae (Rhodophyta) and the glaucophyte algae (Glaucophyta) that store Floridean starch outside the plastids, in the cytoplasm. This clade includes all of the organisms that eons ago acquired their primary chloroplasts directly by engulfing cyanobacteria (e.g., Plantae Cavalier-Smith, 1981).Plant_cell_1_3_2
Old definitions of plant (obsolete)Plant_cell_1_4_0 Plantae sensu amploPlant_cell_1_4_1 Plants in the widest sense refers to older, obsolete classifications that placed diverse algae, fungi or bacteria in Plantae (e.g., Plantae or Vegetabilia Linnaeus, Plantae Haeckel 1866, Metaphyta Haeckel, 1894, Plantae Whittaker, 1969).Plant_cell_1_4_2

Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships. Plant_sentence_23

These are not yet completely settled, but one accepted relationship between the three groups described above is shown below. Plant_sentence_24

Those which have been called "plants" are in bold (some minor groups have been omitted). Plant_sentence_25

The way in which the groups of green algae are combined and named varies considerably between authors. Plant_sentence_26

Algae Plant_section_2

Main article: Algae Plant_sentence_27

Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom. Plant_sentence_28

The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the green algae, red algae and brown algae. Plant_sentence_29

There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, and they are no longer classified as plants as defined here. Plant_sentence_30

The Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. Plant_sentence_31

With a few exceptions, the green plants have the following features in common; primary chloroplasts derived from cyanobacteria containing chlorophylls a and b, cell walls containing cellulose, and food stores in the form of starch contained within the plastids. Plant_sentence_32

They undergo closed mitosis without centrioles, and typically have mitochondria with flat cristae. Plant_sentence_33

The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Plant_sentence_34

Two additional groups, the Rhodophyta (red algae) and Glaucophyta (glaucophyte algae), also have primary chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria, although they differ from Viridiplantae in the pigments which are used in photosynthesis and so are different in colour. Plant_sentence_35

These groups also differ from green plants in that the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. Plant_sentence_36

They appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida, whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event. Plant_sentence_37

This is the broadest modern definition of the term 'plant'. Plant_sentence_38

In contrast, most other algae (e.g. brown algae/diatoms, haptophytes, dinoflagellates, and euglenids) not only have different pigments but also have chloroplasts with three or four surrounding membranes. Plant_sentence_39

They are not close relatives of the Archaeplastida, presumably having acquired chloroplasts separately from ingested or symbiotic green and red algae. Plant_sentence_40

They are thus not included in even the broadest modern definition of the plant kingdom, although they were in the past. Plant_sentence_41

The green plants or Viridiplantae were traditionally divided into the green algae (including the stoneworts) and the land plants. Plant_sentence_42

However, it is now known that the land plants evolved from within a group of green algae, so that the green algae by themselves are a paraphyletic group, i.e. a group that excludes some of the descendants of a common ancestor. Plant_sentence_43

Paraphyletic groups are generally avoided in modern classifications, so that in recent treatments the Viridiplantae have been divided into two clades, the Chlorophyta and the Streptophyta (including the land plants and Charophyta). Plant_sentence_44

The Chlorophyta (a name that has also been used for all green algae) are the sister group to the Charophytes, from which the land plants evolved. Plant_sentence_45

There are about 4,300 species, mainly unicellular or multicellular marine organisms such as the sea lettuce, Ulva. Plant_sentence_46

The other group within the Viridiplantae are the mainly freshwater or terrestrial Streptophyta, which consists of the land plants together with the Charophyta, itself consisting of several groups of green algae such as the desmids and stoneworts. Plant_sentence_47

Streptophyte algae are either unicellular or form multicellular filaments, branched or unbranched. Plant_sentence_48

The genus Spirogyra is a filamentous streptophyte alga familiar to many, as it is often used in teaching and is one of the organisms responsible for the algal "scum" on ponds. Plant_sentence_49

The freshwater stoneworts strongly resemble land plants and are believed to be their closest relatives. Plant_sentence_50

Growing immersed in fresh water, they consist of a central stalk with whorls of branchlets. Plant_sentence_51

Fungi Plant_section_3

Main article: Fungi Plant_sentence_52

Linnaeus' original classification placed the fungi within the Plantae, since they were unquestionably neither animals or minerals and these were the only other alternatives. Plant_sentence_53

With 19th century developments in microbiology, Ernst Haeckel introduced the new kingdom Protista in addition to Plantae and Animalia, but whether fungi were best placed in the Plantae or should be reclassified as protists remained controversial. Plant_sentence_54

In 1969, Robert Whittaker proposed the creation of the kingdom Fungi. Plant_sentence_55

Molecular evidence has since shown that the most recent common ancestor (concestor), of the Fungi was probably more similar to that of the Animalia than to that of Plantae or any other kingdom. Plant_sentence_56

Whittaker's original reclassification was based on the fundamental difference in nutrition between the Fungi and the Plantae. Plant_sentence_57

Unlike plants, which generally gain carbon through photosynthesis, and so are called autotrophs, fungi do not possess chloroplasts and generally obtain carbon by breaking down and absorbing surrounding materials, and so are called heterotrophic saprotrophs. Plant_sentence_58

In addition, the substructure of multicellular fungi is different from that of plants, taking the form of many chitinous microscopic strands called hyphae, which may be further subdivided into cells or may form a syncytium containing many eukaryotic nuclei. Plant_sentence_59

Fruiting bodies, of which mushrooms are the most familiar example, are the reproductive structures of fungi, and are unlike any structures produced by plants. Plant_sentence_60

Diversity Plant_section_4

The table below shows some species count estimates of different green plant (Viridiplantae) divisions. Plant_sentence_61

About 85–90% of all plants are flowering plants. Plant_sentence_62

Several projects are currently attempting to collect all plant species in online databases, e.g. the World Flora Online and World Plants both list about 350,000 species. Plant_sentence_63


Diversity of living green plant (Viridiplantae) divisionsPlant_table_caption_2
Informal groupPlant_header_cell_2_0_0 Division namePlant_header_cell_2_0_1 Common namePlant_header_cell_2_0_2 No. of living speciesPlant_header_cell_2_0_3 Approximate No. in informal groupPlant_header_cell_2_0_4
Green algaePlant_cell_2_1_0 ChlorophytaPlant_cell_2_1_1 green algae (chlorophytes)Plant_cell_2_1_2 3,800–4,300Plant_cell_2_1_3 8,500


CharophytaPlant_cell_2_2_0 green algae (e.g. desmids & stoneworts)Plant_cell_2_2_1 2,800–6,000Plant_cell_2_2_2
BryophytesPlant_cell_2_3_0 MarchantiophytaPlant_cell_2_3_1 liverwortsPlant_cell_2_3_2 6,000–8,000Plant_cell_2_3_3 19,000


AnthocerotophytaPlant_cell_2_4_0 hornwortsPlant_cell_2_4_1 100–200Plant_cell_2_4_2
BryophytaPlant_cell_2_5_0 mossesPlant_cell_2_5_1 12,000Plant_cell_2_5_2
PteridophytesPlant_cell_2_6_0 LycopodiophytaPlant_cell_2_6_1 club mossesPlant_cell_2_6_2 1,200Plant_cell_2_6_3 12,000


PteridophytaPlant_cell_2_7_0 ferns, whisk ferns & horsetailsPlant_cell_2_7_1 11,000Plant_cell_2_7_2
Seed plantsPlant_cell_2_8_0 CycadophytaPlant_cell_2_8_1 cycadsPlant_cell_2_8_2 160Plant_cell_2_8_3 260,000


GinkgophytaPlant_cell_2_9_0 ginkgoPlant_cell_2_9_1 1Plant_cell_2_9_2
PinophytaPlant_cell_2_10_0 conifersPlant_cell_2_10_1 630Plant_cell_2_10_2
GnetophytaPlant_cell_2_11_0 gnetophytesPlant_cell_2_11_1 70Plant_cell_2_11_2
MagnoliophytaPlant_cell_2_12_0 flowering plantsPlant_cell_2_12_1 258,650Plant_cell_2_12_2

The naming of plants is governed by the International Code of Nomenclature for algae, fungi, and plants and International Code of Nomenclature for Cultivated Plants (see cultivated plant taxonomy). Plant_sentence_64

Evolution Plant_section_5

Further information: Evolutionary history of plants Plant_sentence_65

The evolution of plants has resulted in increasing levels of complexity, from the earliest algal mats, through bryophytes, lycopods, ferns to the complex gymnosperms and angiosperms of today. Plant_sentence_66

Plants in all of these groups continue to thrive, especially in the environments in which they evolved. Plant_sentence_67

An algal scum formed on the land  million years ago, but it was not until the Ordovician Period, around  million years ago, that land plants appeared. Plant_sentence_68

However, new evidence from the study of carbon isotope ratios in Precambrian rocks has suggested that complex photosynthetic plants developed on the earth over 1000 m.y.a. Plant_sentence_69

For more than a century it has been assumed that the ancestors of land plants evolved in aquatic environments and then adapted to a life on land, an idea usually credited to botanist Frederick Orpen Bower in his 1908 book The Origin of a Land Flora. Plant_sentence_70

A recent alternative view, supported by genetic evidence, is that they evolved from terrestrial single-celled algae, and that even the common ancestor of red and green algae, and the unicellular freshwater algae glaucophytes, originated in a terrestrial environment in freshwater biofilms or microbial mats. Plant_sentence_71

Primitive land plants began to diversify in the late Silurian Period, around  million years ago, and the results of their diversification are displayed in remarkable detail in an early Devonian fossil assemblage from the Rhynie chert. Plant_sentence_72

This chert preserved early plants in cellular detail, petrified in volcanic springs. Plant_sentence_73

By the middle of the Devonian Period most of the features recognised in plants today are present, including roots, leaves and secondary wood, and by late Devonian times seeds had evolved. Plant_sentence_74

Late Devonian plants had thereby reached a degree of sophistication that allowed them to form forests of tall trees. Plant_sentence_75

Evolutionary innovation continued in the Carboniferous and later geological periods and is ongoing today. Plant_sentence_76

Most plant groups were relatively unscathed by the Permo-Triassic extinction event, although the structures of communities changed. Plant_sentence_77

This may have set the scene for the evolution of flowering plants in the Triassic (~ million years ago), which exploded in the Cretaceous and Tertiary. Plant_sentence_78

The latest major group of plants to evolve were the grasses, which became important in the mid Tertiary, from around  million years ago. Plant_sentence_79

The grasses, as well as many other groups, evolved new mechanisms of metabolism to survive the low CO 2 and warm, dry conditions of the tropics over the last million years. Plant_sentence_80

A 1997 proposed phylogenetic tree of Plantae, after Kenrick and Crane, is as follows, with modification to the Pteridophyta from Smith et al. Plant_sentence_81

The Prasinophyceae are a paraphyletic assemblage of early diverging green algal lineages, but are treated as a group outside the Chlorophyta: later authors have not followed this suggestion. Plant_sentence_82

A newer proposed classification follows Leliaert et al. Plant_sentence_83

2011 and modified with Silar 2016 for the green algae clades and Novíkov & Barabaš-Krasni 2015 for the land plants clade. Plant_sentence_84

Notice that the Prasinophyceae are here placed inside the Chlorophyta. Plant_sentence_85

Later, a phylogeny based on genomes and transcriptomes from 1,153 plant species was proposed. Plant_sentence_86

The placing of algal groups is supported by phylogenies based on genomes from the Mesostigmatophyceae and Chlorokybophyceae that have since been sequenced. Plant_sentence_87

The classification of Bryophyta is supported both by Puttick et al. Plant_sentence_88

2018, and by phylogenies involving the hornwort genomes that have also since been sequenced. Plant_sentence_89

Embryophytes Plant_section_6

Main article: Embryophyte Plant_sentence_90

Fossils Plant_section_7

Main articles: Paleobotany and Evolutionary history of plants Plant_sentence_91

Factors affecting growth Plant_section_8

The genome of a plant controls its growth. Plant_sentence_92

For example, selected varieties or genotypes of wheat grow rapidly, maturing within 110 days, whereas others, in the same environmental conditions, grow more slowly and mature within 155 days. Plant_sentence_93

Growth is also determined by environmental factors, such as temperature, available water, available light, carbon dioxide and available nutrients in the soil. Plant_sentence_94

Any change in the availability of these external conditions will be reflected in the plant's growth and the timing of its development. Plant_sentence_95

Biotic factors also affect plant growth. Plant_sentence_96

Plants can be so crowded that no single individual produces normal growth, causing etiolation and chlorosis. Plant_sentence_97

Optimal plant growth can be hampered by grazing animals, suboptimal soil composition, lack of mycorrhizal fungi, and attacks by insects or plant diseases, including those caused by bacteria, fungi, viruses, and nematodes. Plant_sentence_98

Simple plants like algae may have short life spans as individuals, but their populations are commonly seasonal. Plant_sentence_99

Annual plants grow and reproduce within one growing season, biennial plants grow for two growing seasons and usually reproduce in second year, and perennial plants live for many growing seasons and once mature will often reproduce annually. Plant_sentence_100

These designations often depend on climate and other environmental factors. Plant_sentence_101

Plants that are annual in alpine or temperate regions can be biennial or perennial in warmer climates. Plant_sentence_102

Among the vascular plants, perennials include both evergreens that keep their leaves the entire year, and deciduous plants that lose their leaves for some part of it. Plant_sentence_103

In temperate and boreal climates, they generally lose their leaves during the winter; many tropical plants lose their leaves during the dry season. Plant_sentence_104

The growth rate of plants is extremely variable. Plant_sentence_105

Some mosses grow less than 0.001 millimeters per hour (mm/h), while most trees grow 0.025–0.250 mm/h. Plant_sentence_106

Some climbing species, such as kudzu, which do not need to produce thick supportive tissue, may grow up to 12.5 mm/h. Plant_sentence_107

Plants protect themselves from frost and dehydration stress with antifreeze proteins, heat-shock proteins and sugars (sucrose is common). Plant_sentence_108

LEA (Late Embryogenesis Abundant) protein expression is induced by stresses and protects other proteins from aggregation as a result of desiccation and freezing. Plant_sentence_109

Effects of freezing Plant_section_9

When water freezes in plants, the consequences for the plant depend very much on whether the freezing occurs within cells (intracellularly) or outside cells in intercellular spaces. Plant_sentence_110

Intracellular freezing, which usually kills the cell regardless of the hardiness of the plant and its tissues, seldom occurs in nature because rates of cooling are rarely high enough to support it. Plant_sentence_111

Rates of cooling of several degrees Celsius per minute are typically needed to cause intracellular formation of ice. Plant_sentence_112

At rates of cooling of a few degrees Celsius per hour, segregation of ice occurs in intercellular spaces. Plant_sentence_113

This may or may not be lethal, depending on the hardiness of the tissue. Plant_sentence_114

At freezing temperatures, water in the intercellular spaces of plant tissue freezes first, though the water may remain unfrozen until temperatures drop below −7 °C (19 °F). Plant_sentence_115

After the initial formation of intercellular ice, the cells shrink as water is lost to the segregated ice, and the cells undergo freeze-drying. Plant_sentence_116

This dehydration is now considered the fundamental cause of freezing injury. Plant_sentence_117

DNA damage and repair Plant_section_10

Plants are continuously exposed to a range of biotic and abiotic stresses. Plant_sentence_118

These stresses often cause DNA damage directly, or indirectly via the generation of reactive oxygen species. Plant_sentence_119

Plants are capable of a DNA damage response that is a critical mechanism for maintaining genome stability. Plant_sentence_120

The DNA damage response is particularly important during seed germination, since seed quality tends to deteriorate with age in association with DNA damage accumulation. Plant_sentence_121

During germination repair processes are activated to deal with this accumulated DNA damage. Plant_sentence_122

In particular, single- and double-strand breaks in DNA can be repaired. Plant_sentence_123

The DNA checkpoint kinase ATM has a key role in integrating progression through germination with repair responses to the DNA damages accumulated by the aged seed. Plant_sentence_124

Plant cells Plant_section_11

Main article: Plant cell Plant_sentence_125

Plant cells are typically distinguished by their large water-filled central vacuole, chloroplasts, and rigid cell walls that are made up of cellulose, hemicellulose, and pectin. Plant_sentence_126

Cell division is also characterized by the development of a phragmoplast for the construction of a cell plate in the late stages of cytokinesis. Plant_sentence_127

Just as in animals, plant cells differentiate and develop into multiple cell types. Plant_sentence_128

Totipotent meristematic cells can differentiate into vascular, storage, protective (e.g. epidermal layer), or reproductive tissues, with more primitive plants lacking some tissue types. Plant_sentence_129

Physiology Plant_section_12

Main article: Plant physiology Plant_sentence_130

Photosynthesis Plant_section_13

Main articles: Photosynthesis and Biological pigment Plant_sentence_131

Plants are photosynthetic, which means that they manufacture their own food molecules using energy obtained from light. Plant_sentence_132

The primary mechanism plants have for capturing light energy is the pigment chlorophyll. Plant_sentence_133

All green plants contain two forms of chlorophyll, chlorophyll a and chlorophyll b. Plant_sentence_134

The latter of these pigments is not found in red or brown algae. Plant_sentence_135

The simple equation of photosynthesis is as follows: Plant_sentence_136

Immune system Plant_section_14

See also: Immune system and Plant disease resistance Plant_sentence_137

By means of cells that behave like nerves, plants receive and distribute within their systems information about incident light intensity and quality. Plant_sentence_138

Incident light that stimulates a chemical reaction in one leaf, will cause a chain reaction of signals to the entire plant via a type of cell termed a bundle sheath cell. Plant_sentence_139

Researchers, from the Warsaw University of Life Sciences in Poland, found that plants have a specific memory for varying light conditions, which prepares their immune systems against seasonal pathogens. Plant_sentence_140

Plants use pattern-recognition receptors to recognize conserved microbial signatures. Plant_sentence_141

This recognition triggers an immune response. Plant_sentence_142

The first plant receptors of conserved microbial signatures were identified in rice (XA21, 1995) and in Arabidopsis thaliana (FLS2, 2000). Plant_sentence_143

Plants also carry immune receptors that recognize highly variable pathogen effectors. Plant_sentence_144

These include the NBS-LRR class of proteins. Plant_sentence_145

Internal distribution Plant_section_15

Main article: Vascular tissue Plant_sentence_146

Vascular plants differ from other plants in that nutrients are transported between their different parts through specialized structures, called xylem and phloem. Plant_sentence_147

They also have roots for taking up water and minerals. Plant_sentence_148

The xylem moves water and minerals from the root to the rest of the plant, and the phloem provides the roots with sugars and other nutrient produced by the leaves. Plant_sentence_149

Genomics Plant_section_16

Plants have some of the largest genomes among all organisms. Plant_sentence_150

The largest plant genome (in terms of gene number) is that of wheat (Triticum asestivum), predicted to encode ≈94,000 genes and thus almost 5 times as many as the human genome. Plant_sentence_151

The first plant genome sequenced was that of Arabidopsis thaliana which encodes about 25,500 genes. Plant_sentence_152

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 Norway Spruce (Picea abies), extends over 19,600 Mb (encoding about 28,300 genes). Plant_sentence_153

Ecology Plant_section_17

Main article: Plant ecology Plant_sentence_154

The photosynthesis conducted by land plants and algae is the ultimate source of energy and organic material in nearly all ecosystems. Plant_sentence_155

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% oxygen. Plant_sentence_156

Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively rare anaerobic environments. Plant_sentence_157

Plants are the primary producers in most terrestrial ecosystems and form the basis of the food web in those ecosystems. Plant_sentence_158

Many animals rely on plants for shelter as well as oxygen and food. Plant_sentence_159

Plants form about 80% of the world biomass at about 450 gigatonnes (4.4×10 long tons; 5.0×10 short tons) of carbon. Plant_sentence_160

Land plants are key components of the water cycle and several other biogeochemical cycles. Plant_sentence_161

Some plants have coevolved with nitrogen fixing bacteria, making plants an important part of the nitrogen cycle. Plant_sentence_162

Plant roots play an essential role in soil development and the prevention of soil erosion. Plant_sentence_163

Distribution Plant_section_18

Plants are distributed almost worldwide. Plant_sentence_164

While they inhabit a multitude of biomes and ecoregions, few can be found beyond the tundras at the northernmost regions of continental shelves. Plant_sentence_165

At the southern extremes, plants of the Antarctic flora have adapted tenaciously to the prevailing conditions. Plant_sentence_166

Plants are often the dominant physical and structural component of habitats where they occur. Plant_sentence_167

Many of the Earth's biomes are named for the type of vegetation because plants are the dominant organisms in those biomes, such as grasslands, taiga and tropical rainforest. Plant_sentence_168

Ecological relationships Plant_section_19

Food Plant_section_20

Main article: Agriculture Plant_sentence_169

Humans depend on plants for food, either directly or as feed for domestic animals. Plant_sentence_170

Agriculture deals with the production of food crops, and has played a key role in the history of world civilizations. Plant_sentence_171

Agriculture includes agronomy for arable crops, horticulture for vegetables and fruit, and forestry for timber. Plant_sentence_172

About 7,000 species of plant have been used for food, though most of today's food is derived from only 30 species. Plant_sentence_173

The major staples include cereals such as rice and wheat, starchy roots and tubers such as cassava and potato, and legumes such as peas and beans. Plant_sentence_174

Vegetable oils such as olive oil provide lipids, while fruit and vegetables contribute vitamins and minerals to the diet. Plant_sentence_175

Medicines Plant_section_21

Main article: Medicinal plants Plant_sentence_176

Medicinal plants are a primary source of organic compounds, both for their medicinal and physiological effects, and for the industrial synthesis of a vast array of organic chemicals. Plant_sentence_177

Many hundreds of medicines are derived from plants, both traditional medicines used in herbalism and chemical substances purified from plants or first identified in them, sometimes by ethnobotanical search, and then synthesised for use in modern medicine. Plant_sentence_178

Modern medicines derived from plants include aspirin, taxol, morphine, quinine, reserpine, colchicine, digitalis and vincristine. Plant_sentence_179

Plants used in herbalism include ginkgo, echinacea, feverfew, and Saint John's wort. Plant_sentence_180

The pharmacopoeia of Dioscorides, De Materia Medica, describing some 600 medicinal plants, was written between 50 and 70 AD and remained in use in Europe and the Middle East until around 1600 AD; it was the precursor of all modern pharmacopoeias. Plant_sentence_181

Nonfood products Plant_section_22

Plants grown as industrial crops are the source of a wide range of products used in manufacturing, sometimes so intensively as to risk harm to the environment. Plant_sentence_182

Nonfood products include essential oils, natural dyes, pigments, waxes, resins, tannins, alkaloids, amber and cork. Plant_sentence_183

Products derived from plants include soaps, shampoos, perfumes, cosmetics, paint, varnish, turpentine, rubber, latex, lubricants, linoleum, plastics, inks, and gums. Plant_sentence_184

Renewable fuels from plants include firewood, peat and other biofuels. Plant_sentence_185

The fossil fuels coal, petroleum and natural gas are derived from the remains of aquatic organisms including phytoplankton in geological time. Plant_sentence_186

Structural resources and fibres from plants are used to construct dwellings and to manufacture clothing. Plant_sentence_187

Wood is used not only for buildings, boats, and furniture, but also for smaller items such as musical instruments and sports equipment. Plant_sentence_188

Wood is pulped to make paper and cardboard. Plant_sentence_189

Cloth is often made from cotton, flax, ramie or synthetic fibres such as rayon and acetate derived from plant cellulose. Plant_sentence_190

Thread used to sew cloth likewise comes in large part from cotton. Plant_sentence_191

Aesthetic uses Plant_section_23

Thousands of plant species are cultivated for aesthetic purposes as well as to provide shade, modify temperatures, reduce wind, abate noise, provide privacy, and prevent soil erosion. Plant_sentence_192

Plants are the basis of a multibillion-dollar per year tourism industry, which includes travel to historic gardens, national parks, rainforests, forests with colorful autumn leaves, and festivals such as Japan's and America's cherry blossom festivals. Plant_sentence_193

While some gardens are planted with food crops, many are planted for aesthetic, ornamental, or conservation purposes. Plant_sentence_194

Arboretums and botanical gardens are public collections of living plants. Plant_sentence_195

In private outdoor gardens, lawn grasses, shade trees, ornamental trees, shrubs, vines, herbaceous perennials and bedding plants are used. Plant_sentence_196

Gardens may cultivate the plants in a naturalistic state, or may sculpture their growth, as with topiary or espalier. Plant_sentence_197

Gardening is the most popular leisure activity in the U.S., and working with plants or horticulture therapy is beneficial for rehabilitating people with disabilities. Plant_sentence_198

Plants may also be grown or kept indoors as houseplants, or in specialized buildings such as greenhouses that are designed for the care and cultivation of living plants. Plant_sentence_199

Venus Flytrap, sensitive plant and resurrection plant are examples of plants sold as novelties. Plant_sentence_200

There are also art forms specializing in the arrangement of cut or living plant, such as bonsai, ikebana, and the arrangement of cut or dried flowers. Plant_sentence_201

Ornamental plants have sometimes changed the course of history, as in tulipomania. Plant_sentence_202

Architectural designs resembling plants appear in the capitals of Ancient Egyptian columns, which were carved to resemble either the Egyptian white lotus or the papyrus. Plant_sentence_203

Images of plants are often used in painting and photography, as well as on textiles, money, stamps, flags and coats of arms. Plant_sentence_204

Scientific and cultural uses Plant_section_24

Basic biological research has often been done with plants. Plant_sentence_205

In genetics, the breeding of pea plants allowed Gregor Mendel to derive the basic laws governing inheritance, and examination of chromosomes in maize allowed Barbara McClintock to demonstrate their connection to inherited traits. Plant_sentence_206

The plant Arabidopsis thaliana is used in laboratories as a model organism to understand how genes control the growth and development of plant structures. Plant_sentence_207

NASA predicts that space stations or space colonies will one day rely on plants for life support. Plant_sentence_208

Ancient trees are revered and many are famous. Plant_sentence_209

Tree rings themselves are an important method of dating in archeology, and serve as a record of past climates. Plant_sentence_210

Plants figure prominently in mythology, religion and literature. Plant_sentence_211

They are used as national and state emblems, including state trees and state flowers. Plant_sentence_212

Plants are often used as memorials, gifts and to mark special occasions such as births, deaths, weddings and holidays. Plant_sentence_213

The arrangement of flowers may be used to send hidden messages. Plant_sentence_214

Negative effects Plant_section_25

Weeds are unwanted plants growing in managed environments such as farms, urban areas, gardens, lawns, and parks. Plant_sentence_215

People have spread plants beyond their native ranges and some of these introduced plants become invasive, damaging existing ecosystems by displacing native species, and sometimes becoming serious weeds of cultivation. Plant_sentence_216

Plants may cause harm to animals, including people. Plant_sentence_217

Plants that produce windblown pollen invoke allergic reactions in people who suffer from hay fever. Plant_sentence_218

A wide variety of plants are poisonous. Plant_sentence_219

Toxalbumins are plant poisons fatal to most mammals and act as a serious deterrent to consumption. Plant_sentence_220

Several plants cause skin irritations when touched, such as poison ivy. Plant_sentence_221

Certain plants contain psychotropic chemicals, which are extracted and ingested or smoked, including nicotine from tobacco, cannabinoids from Cannabis sativa, cocaine from Erythroxylon coca and opium from opium poppy. Plant_sentence_222

Smoking causes damage to health or even death, while some drugs may also be harmful or fatal to people. Plant_sentence_223

Both illegal and legal drugs derived from plants may have negative effects on the economy, affecting worker productivity and law enforcement costs. Plant_sentence_224

See also Plant_section_26

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