Plantae

Plants
Fossil range: Cambrian to recent, but see text

Scientific classification
Domain:Eukaryota
(unranked)Archaeplastida
Kingdom:Plantae
Haeckel, 1866[1]
Divisions


Green algae Land plants (embryophytes) Nematophytes


Plants are a major group of life forms and include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae. About 350,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies, are estimated to exist currently. As of 2004, some 287,655 species had been identified, of which 258,650 are flowering and 15,000 bryophytes. Green plants, sometimes called metaphytes, obtain most of their energy from sunlight via a process called photosynthesis.

Definition

Aristotle divided all living things between plants (which generally do not move), and animals (which often are mobile to catch their food). In Linnaeus' system, these became the Kingdoms Vegetabilia (later Metaphyta or Plantae) and Animalia (also called Metazoa). Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae were removed to new kingdoms. However, these are still often considered plants in many contexts, both technical and popular. Indeed, an attempt to perfectly match "plant" with a single taxon is problematic, because for most people the term "plant" is only vaguely related to the phylogenic concepts on which modern taxonomy and systematics are based.

When the name Plantae is applied to a specific taxon, it is usually referring to one of three concepts. From smallest to largest in inclusiveness, these three groupings are: Informally, other creatures that carry out photosynthesis are called plants as well, but they do not constitute a formal taxon and represent species that are not closely related to true plants. There are around about 375,000 species (types) of plants, and each year more are found and described by science.

Algae

Main article: Algae


The algae comprise several different groups of organisms that produce energy through photosynthesis. However, most are not classified within the Kingdom Plantae but in the Kingdom Protista. Most conspicuous are the seaweeds, multicellular algae that may roughly resemble terrestrial plants, but are classified among the green, red, and brown algae. These and other algal groups also include various single-celled organisms.

The embryophytes developed from green algae (Chlorophyta); the two groups are collectively referred to as the green plants or Viridiplantae. The Kingdom Plantae is often taken to mean this monophyletic grouping. With a few exceptions among the green algae, all such forms have cell walls containing cellulose and chloroplasts containing chlorophylls a and b, and store food in the form of starch. They undergo closed mitosis without centrioles, and typically have mitochondria with flat cristae.

The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. The same is true of the red algae, and the two groups are generally believed to have a common origin (see Archaeplastida). In contrast, most other algae have chloroplasts with three or four membranes. They are not close relatives of the green plants, presumably in origin acquiring chloroplasts separately from ingested or symbiotic green and red algae.

Fungi

Main article: Fungi


Fungi are no longer considered to be plants, though they were previously included in the plant kingdom. Unlike embryophytes and algae, fungi are not photosynthetic, but are saprotrophs: obtaining food by breaking down and absorbing surrounding materials. Fungi are not plants, but were historically treated as closely related to plants, and were considered to be in the purview of botanists. It has long been recognized that fungi are evolutionarily closer to animals than to plants, but they still are covered more in depth in introductory botany courses and are not necessarily touched upon in introductory zoology courses. Most fungi are formed by microscopic structures called hyphae, which may or may not be divided into cells but contain eukaryotic nuclei. Fruiting bodies, of which mushrooms are most familiar, are the reproductive structures of fungi. They are not related to any of the photosynthetic groups, but are close relatives of animals. Therefore, the fungi are in a kingdom of their own.

Diversity

About 350,000 species of plants, defined as seed plants, bryophytes, ferns and fern allies, are estimated to exist currently. As of 2004, some 287,655 species had been identified, of which 258,650 are flowering plants, 16,000 bryophytes, 11,000 ferns and 8,000 green algae.

Diversity of living plant divisions
Informal group Division name Common name No. of living species
Green algaeChlorophytagreen algae (chlorophytes)3,800 [2]
Charophytagreen algae (desmids & charophytes)4,000 - 6,000 [3]
BryophytesMarchantiophytaliverworts6,000 - 8,000 [4]
Anthocerotophytahornworts100 - 200 [5]
Bryophytamosses10,000 [6]
PteridophytesLycopodiophytaclub mosses1,200 [7]
Pteridophytaferns, whisk ferns & horsetails11,000 <ref name="Raven 2005" />
Seed plantsCycadophytacycads160 [8]
Ginkgophytaginkgo1 [9]
Pinophytaconifers630 <ref name="Raven 2005" />
Gnetophytagnetophytes70 <ref name="Raven 2005" />
Magnoliophytaflowering plants258,650 [10]

Phylogeny

A proposed phylogeny of the Plantae after Kenrick and Crane[11] is as follows, with modification to the Pteridophyta from Smith et al.[12] The Prasinophyceae may be a paraphyletic basal group to all green plants.



Prasinophyceae (micromonads)


Streptobionta

Embryophytes

Stomatophytes

Polysporangiates

Tracheophytes
Eutracheophytes
Euphyllophytina
Lignophytia

Spermatophytes (seed plants)


Progymnospermophyta †


Pteridophyta


Pteridopsida (true ferns)


Marattiopsida


Equisetopsida (horsetails)


Psilotopsida (whisk ferns & adders'-tongues)


Cladoxylopsida †




Lycophytina

Lycopodiophyta


Zosterophyllophyta †




Rhyniophyta †




Aglaophyton †


Horneophytopsida †




Bryophyta (mosses)


Anthocerotophyta (hornworts)




Marchantiophyta (liverworts)




Charophyta




Chlorophyta


Trebouxiophyceae (Pleurastrophyceae)


Chlorophyceae



Ulvophyceae




Embryophytes

''Main article: [[

Prasinophyceae (micromonads)


Streptobionta

Embryophytes

Stomatophytes

Polysporangiates

Tracheophytes
Eutracheophytes
Euphyllophytina
Lignophytia

Spermatophytes (seed plants)


Progymnospermophyta †


Pteridophyta


Pteridopsida (true ferns)


Marattiopsida


Equisetopsida (horsetails)


Psilotopsida (whisk ferns & adders'-tongues)


Cladoxylopsida †




Lycophytina

Lycopodiophyta


Zosterophyllophyta †




Rhyniophyta †




Aglaophyton †


Horneophytopsida †




Bryophyta (mosses)


Anthocerotophyta (hornworts)




Marchantiophyta (liverworts)




Charophyta




Chlorophyta


Trebouxiophyceae (Pleurastrophyceae)


Chlorophyceae



Ulvophyceae



|

Prasinophyceae (micromonads)


Streptobionta

Embryophytes

Stomatophytes

Polysporangiates

Tracheophytes
Eutracheophytes
Euphyllophytina
Lignophytia

Spermatophytes (seed plants)


Progymnospermophyta †


Pteridophyta


Pteridopsida (true ferns)


Marattiopsida


Equisetopsida (horsetails)


Psilotopsida (whisk ferns & adders'-tongues)


Cladoxylopsida †




Lycophytina

Lycopodiophyta


Zosterophyllophyta †




Rhyniophyta †




Aglaophyton †


Horneophytopsida †




Bryophyta (mosses)


Anthocerotophyta (hornworts)




Marchantiophyta (liverworts)




Charophyta




Chlorophyta


Trebouxiophyceae (Pleurastrophyceae)


Chlorophyceae



Ulvophyceae



]]''
Most familiar are the multicellular land plants, called embryophytes. They include the vascular plants, plants with full systems of leaves, stems, and roots. They also include a few of their close relatives, often called bryophytes, of which mosses and liverworts are the most common.

All of these plants have eukaryotic cells with cell walls composed of cellulose, and most obtain their energy through photosynthesis, using light and carbon dioxide to synthesize food. About three hundred plant species do not photosynthesize but are parasites on other species of photosynthetic plants. Plants are distinguished from green algae, which represent a mode of photosynthetic life similar to the kind modern plants are believed to have evolved from, by having specialized reproductive organs protected by non-reproductive tissues.

Bryophytes first appeared during the early Palaeozoic. They can only survive where moisture is available for significant periods, although some species are desiccation tolerant. Most species of bryophyte remain small throughout their life-cycle. This involves an alternation between two generations: a haploid stage, called the gametophyte, and a diploid stage, called the sporophyte. The sporophyte is short-lived and remains dependent on its parent gametophyte.

Vascular plants first appeared during the Silurian period, and by the Devonian had diversified and spread into many different land environments. They have a number of adaptations that allowed them to overcome the limitations of the bryophytes. These include a cuticle resistant to desiccation, and vascular tissues which transport water throughout the organism. In most the sporophyte acts as a separate individual, while the gametophyte remains small.

The first primitive seed plants, Pteridosperms (seed ferns) and Cordaites, both groups now extinct, appeared in the late Devonian and diversified through the Carboniferous, with further evolution through the Permian and Triassic periods. In these the gametophyte stage is completely reduced, and the sporophyte begins life inside an enclosure called a seed, which develops while on the parent plant, and with fertilisation by means of pollen grains. Whereas other vascular plants, such as ferns, reproduce by means of spores and so need moisture to develop, some seed plants can survive and reproduce in extremely arid conditions.

Early seed plants are referred to as gymnosperms (naked seeds), as the seed embryo is not enclosed in a protective structure at pollination, with the pollen landing directly on the embryo. Four surviving groups remain widespread now, particularly the conifers, which are dominant trees in several biomes. The angiosperms, comprising the flowering plants, were the last major group of plants to appear, emerging from within the gymnosperms during the Jurassic and diversifying rapidly during the Cretaceous. These differ in that the seed embryo (angiosperm) is enclosed, so the pollen has to grow a tube to penetrate the protective seed coat; they are the predominant group of flora in most biomes today.

Fossils

''Main articles: [[

Prasinophyceae (micromonads)


Streptobionta

Embryophytes

Stomatophytes

Polysporangiates

Tracheophytes
Eutracheophytes
Euphyllophytina
Lignophytia

Spermatophytes (seed plants)


Progymnospermophyta †


Pteridophyta


Pteridopsida (true ferns)


Marattiopsida


Equisetopsida (horsetails)


Psilotopsida (whisk ferns & adders'-tongues)


Cladoxylopsida †




Lycophytina

Lycopodiophyta


Zosterophyllophyta †




Rhyniophyta †




Aglaophyton †


Horneophytopsida †




Bryophyta (mosses)


Anthocerotophyta (hornworts)




Marchantiophyta (liverworts)




Charophyta




Chlorophyta


Trebouxiophyceae (Pleurastrophyceae)


Chlorophyceae



Ulvophyceae



|

Prasinophyceae (micromonads)


Streptobionta

Embryophytes

Stomatophytes

Polysporangiates

Tracheophytes
Eutracheophytes
Euphyllophytina
Lignophytia

Spermatophytes (seed plants)


Progymnospermophyta †


Pteridophyta


Pteridopsida (true ferns)


Marattiopsida


Equisetopsida (horsetails)


Psilotopsida (whisk ferns & adders'-tongues)


Cladoxylopsida †




Lycophytina

Lycopodiophyta


Zosterophyllophyta †




Rhyniophyta †




Aglaophyton †


Horneophytopsida †




Bryophyta (mosses)


Anthocerotophyta (hornworts)




Marchantiophyta (liverworts)




Charophyta




Chlorophyta


Trebouxiophyceae (Pleurastrophyceae)


Chlorophyceae



Ulvophyceae



]], Plant fossil, and Evolutionary history of plants''
Enlarge picture
A petrified log in Petrified Forest National Park.
Plant fossils include roots, wood, leaves, seeds, fruit, pollen, spores, phytoliths, and amber (the fossilized resin produced by some plants). Fossil land plants are recorded in terrestrial, lacustrine, fluvial and nearshore marine sediments. Pollen, spores and algae (dinoflagellates and acritarchs) are used for dating sedimentary rock sequences. The remains of fossil plants are not as common as fossil animals, although plant fossils are locally abundant in many regions worldwide.

The earliest fossils clearly assignable to Kingdom Plantae are fossil green algae from the Cambrian. These fossils resemble calcified multicellular members of the Dasycladales. Earlier Precambrian fossils are known which resemble single-cell green algae, but definitive identity with that group of algae is uncertain.

The oldest known trace fossils of embryophytes date from the Ordovician, though such fossils are fragmentary. By the Silurian, fossils of whole plants are preserved, including the lycophyte Baragwanathia longifolia. From the Devonian, detailed fossils of rhyniophytes have been found. Early fossils of these ancient plants show the individual cells within the plant tissue. The Devonian period also saw the evolution of what many believe to be the first modern tree, Archaeopteris. This fern-like tree combined a woody trunk with the fronds of a fern, but produced no seeds.

The Coal Measures are a major source of Palaeozoic plant fossils, with many groups of plants in existence at this time. The spoil heaps of coal mines are the best places to collect; coal itself is the remains of fossilised plants, though structural detail of the plant fossils is rarely visible in coal. In the Fossil Forest at Victoria Park in Glasgow, Scotland, the stumps of Lepidodendron trees are found in their original growth positions.

The fossilized remains of conifer and angiosperm roots, stems and branches may be locally abundant in lake and inshore sedimentary rocks from the Mesozoic and Caenozoic eras. Sequoia and its allies, magnolia, oak, and palms are often found.

Petrified wood is common in some parts of the world, and is most frequently found in arid or desert areas where it is more readily exposed by erosion. Petrified wood is often heavily silicified (the organic material replaced by silicon dioxide), and the impregnated tissue is often preserved in fine detail. Such specimens may be cut and polished using lapidary equipment. Fossil forests of petrified wood have been found in all continents.

Fossils of seed ferns such as Glossopteris are widely distributed throughout several continents of the southern hemisphere, a fact that gave support to Alfred Wegener's early ideas regarding Continental drift theory.

Life processes

Growth

Most of the solid material in a plant is taken from the atmosphere. Through a process known as photosynthesis, plants use the energy in sunlight to convert carbon dioxide from the atmosphere into simple sugars. These sugars are then used as building blocks and form the main structural component of the plant. Plants rely on soil primarily for support and water (in quantitative terms), but also obtain nitrogen, phosphorus and other crucial elemental nutrients. For the majority of plants to grow successfully they also require oxygen in the atmosphere (for respiration in the dark) and oxygen around their roots. However, a few specialized vascular plants, such as Mangroves, can grow with their roots in anoxic conditions.

Enlarge picture
The leaf is the primary site of photosynthesis in plants.

Factors affecting growth

The genotype of a plant affects its growth, for example selected varieties of wheat grow rapidly, maturing within 110 days, whereas others, in the same environmental conditions, grow more slowly and mature within 155 days.[13]

Growth is also determined by environmental factors, such as temperature, available water, available light, and available nutrients in the soil. Any change in the availability of these external conditions will be reflected in the plants growth.

Biotic factors (living organisms) also affect plant growth.
  • Plants compete with other plants for space, water, light and nutrients. Plants can be so crowded that no single individual makes normal growth.[13]
  • Many plants rely on birds and insects to affect pollination.
  • Grazing animals may completely affect vegetation.
  • Soil fertility is influenced by the activity of bacteria and fungi.
  • Bacteria, fungi, viruses, nematodes and insects can parasitise plants.
  • Some plant roots require an association with fungi to maintain normal activity (mycorrhizal association).[13]
Simple plants like algae may have short life spans as individuals, but their populations are commonly seasonal. Other plants may be organized according to their seasonal growth pattern:
  • Annual: live and reproduce within one growing season.
  • Biennial: live for two growing seasons; usually reproduce in second year.
  • Perennial: live for many growing seasons; continue to reproduce once mature.
Among the vascular plants, perennials include both evergreens that keep their leaves the entire year, and deciduous plants which lose their leaves for some part. In temperate and boreal climates, they generally lose their leaves during the winter; many tropical plants lose their leaves during the dry season.

The growth rate of plants is extremely variable. Some mosses grow less than 0.001 mm/h, while most trees grow 0.025-0.250 mm/h. Some climbing species, such as kudzu, which do not need to produce thick supportive tissue, may grow up to 12.5 mm/h.

Plants protect themselves from frost and dehydration stress with antifreeze proteins, heat-shock proteins and sugars (sucrose is common). LEA (Late Embryogenesis Abundant) protein expression is induced by stresses and protects other proteins from aggregation as a result of desiccation and freezing.[14]

Internal distribution

Enlarge picture
Photographs showing xylem elements in the shoot of a fig tree (Ficus alba): crushed in hydrochloric acid, between slides and cover slips.
Nutrients and water from the soil and the organic compound produces in leaves are distributed to specific areas in the plant through the xylem and phloem. The xylem draws water and nutrients up from the roots to the upper sections of the plant's body, and the phloem conducts other materials, such as the glucose produced during photosynthesis, which gives the plant energy to keep growing and seeding.

The xylem consists of tracheids, which are dead hard-walled cells arranged to form tiny tubes to function in water transport. A tracheid cell wall usually contains the polymer lignin. The phloem however consists of living cells called sieve-tube members. Between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through. Sieve-tube members lack such organs as nuclei or ribosomes, but cells next to them, the companion cells, function to keep the sieve-tube members alive.

Movement of nutrients, water, sugars and waste is effected by transpiration, conduction and absorption.

Transpiration

The most abundant compound in most plants is water, serving a large role in the various processes taking place. Transpiration is the main process a plant can call upon to move compounds within its tissues. The basic minerals and nutrients a plant is composed of remain, generally, within the plant. Water, however, is constantly being lost from the plant through its metabolic and photosynthetic processes to the atmosphere.

Water is transpired from the plants leaves via stomata, carried there via leaf veins and vascular bundles within the plants cambium layer. The movement of water out of the leaf stomata creates, when the leaves are considered collectively, a transpiration pull. The pull is created through water surface tension within the plant cells. The draw of water upwards is assisted by the movement of water into the roots via osmosis. This process also assists the plant in absorbing nutrients from the soil as soluble salts, a process known as absorption.

Absorption

Xylem cells move water and nutrient solutions upwards towards other plant organs from the roots and fine root hairs. Living roots cells actively absorb water in the absence of transpiration pull via osmosis creating root pressure. There are times when plants do not have transpiration pull, usually due to lack of light or other environmental elements. Water in the plant tissues may move to the roots to assist in passive absorption.

Conduction

Xylem and phloem tissues are involved in the conduction processes within plants. The movement of foods throughout the plant takes place mainly in the phloem. Plant conduction (food movement) is from an area of high food content, place of manufacture (photosynthesis) or storage, to a place of food utilisation, or from a point of manufacture to storage tissues. Mineral salts are translocated in the xylem tissues.[14]

Ecology

Main article: Ecology


The photosynthesis conducted by land plants and algae is the ultimate source of energy and organic material in nearly all ecosystems. Photosynthesis radically changed the composition of the early Earth's atmosphere, which as a result is now 21% oxygen. Animals and most other organisms are aerobic, relying on oxygen; those that do not are confined to relatively rare anaerobic environments. Plants are the primary producers in most terrestrial ecosystems and form the basis of the food web in those ecosystems. Many animals rely on plants for shelter as well as oxygen and food.

Land plants are key components of the water cycle and several other biogeochemical cycles. Some plants have coevolved with nitrogen fixing bacteria, making plants an important part of the nitrogen cycle. Plant roots play an essential role in soil development and prevention of soil erosion.

Distribution

Plants are distributed worldwide in varying numbers. While they inhabit a multitude of biomes and ecoregions, few can be found beyond the tundras at the northernmost regions of continental shelves. At the southern extremes, plants have adapted tenaciously to the prevailing conditions. (See Antarctic flora.)

Plants are often the dominant physical and structural component of 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 grasslands and forests.

Ecological relationships

Enlarge picture
The Venus Flytrap, a species of carnivorous plant.
Numerous animals have coevolved with plants. Many animals pollinate flowers in exchange for food in the form of pollen or nectar. Many animals disperse seeds, often by eating fruit and passing the seeds in their feces. 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 provide organic fertilizer.

The majority of plant species have various kinds of fungi associated with their root systems in a kind of 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. Some plants serve as homes for endophytic fungi that protect the plant from herbivores by producing toxins. The fungal endophyte, Neotyphodium coenophialum, in tall fescue (Festuca arundinacea) does tremendous economic damage to the cattle industry in the U.S.

Various forms of parasitism are also fairly common among plants, 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, so have no chlorophyll. Some plants, known as myco-heterotrophs, parasitize mycorrhizal fungi, and hence act as epiparasites on other plants.

Many plants are epiphytes, meaning they grow on other plants, usually trees, without parasitizing them. Epiphytes may indirectly harm their host plant by intercepting mineral nutrients and light that the host would otherwise receive. The weight of large numbers of epiphytes may break tree limbs. Many orchids, bromeliads, ferns and mosses often grow as epiphytes. Bromeliad epiphytes accumulate water in leaf axils to form phytotelmata, complex aquatic food webs.[15]

A few plants are carnivorous, such as the Venus Flytrap and sundew. They trap small animals and digest them to obtain mineral nutrients, especially nitrogen.

Importance

Enlarge picture
Potato plant. Potatoes spread to the rest of the world after European contact with the Americas in the late 1400s and early 1500s and have since become an important field crop.
Enlarge picture
Timber in storage for later processing at a sawmill.
Enlarge picture
A section of a Yew branch showing 27 annual growth rings, pale sapwood and dark heartwood, and pith (centre dark spot). The dark radial lines are small knots.
The study of plant uses by people is termed economic botany or ethnobotany. They are often used as synonyms but some consider economic botany to focus mainly on uses of modern cultivated plants, while ethnobotany studies uses of indigenous plants by native peoples. Human cultivation of plants is part of agriculture, which is the basis of human civilization. Plant agriculture is subdivided into agronomy, horticulture and forestry.

Food

Virtually all human nutrition depends on land plants directly or indirectly. Much of human nutrition depends on cereals, especially maize or corn, wheat and rice or other staple crops such as potato, cassava, and legumes. Other parts from plants that are eaten include fruits, vegetables, nuts, herbs, spices and edible flowers. Beverages from plants include coffee, tea, wine, beer and alcohol. Sugar is obtained mainly from sugar cane and sugar beet. Cooking oils and margarine come from corn, soybean, canola, safflower, sunflower, olive and others. Food additives include gum arabic, guar gum, locust bean gum, starch and pectin.

Nonfood products

Wood is used for buildings, furniture, paper, cardboard, musical instruments and sports equipment. Cloth is often made from cotton, flax or synthetic fibers derived from cellulose, such as rayon and acetate. Renewable fuels from plants include firewood, peat and many other biofuels. Coal and petroleum are fossil fuels derived from plants. Medicines derived from plants include aspirin, taxol, morphine, quinine, reserpine, colchicine, digitalis and vincristine. There are hundreds of herbal supplements such as ginkgo, Echinacea, feverfew, and Saint John's wort. Pesticides derived from plants include nicotine, rotenone, strychnine and pyrethrins. Drugs obtained from plants include opium, cocaine and marijuana. Poisons from plants include ricin, hemlock and curare. Plants are the source of many natural products such as fibers, essential oils, dyes, pigments, waxes, tannins, latex, gums, resins, alkaloids, amber and cork. Products derived from plants include soaps, paints, shampoos, perfumes, cosmetics, turpentine, rubber, varnish, lubricants, linoleum, plastics, inks, chewing gum and hemp rope. Plants are also a primary source of basic chemicals for the industrial synthesis of a vast array of organic chemicals. These chemicals are used in a vast variety of studies and experiments.

Aesthetic uses

Thousands of plant species are cultivated to beautify the human environment as well as to provide shade, modify temperatures, reduce windspeed, abate noise, provide privacy and prevent soil erosion. People use cut flowers, dried flowers and house plants indoors. Outdoors, they use lawngrasses, shade trees, ornamental trees, shrubs, vines, herbaceous perennials and bedding plants. Images of plants are often used in art, architecture, humor, language and photography and on textiles, money, stamps, flags and coats of arms. Living plant art forms include topiary, bonsai, ikebana and espalier. Ornamental plants have sometimes changed the course of history, as in tulipomania. Plants are the basis of a multi-billion dollar per year tourism industry which includes travel to arboretums, botanical gardens, historic gardens, national parks, tulip festivals, rainforests, forests with colorful autumn leaves and the National Cherry Blossom Festival. Venus flytrap, sensitive plant and resurrection plant are examples of plants sold as novelties.

Scientific and cultural uses

Tree rings are an important method of dating in archeology and serve as a record of past climates. Basic biological research has often been done with plants, such as the pea plants used to derive Gregor Mendel's laws of genetics. Space stations or space colonies may one day rely on plants for life support. Plants are used as national and state emblems, including state trees and state flowers. Ancient trees are revered and many are famous. Numerous world records are held by plants. Plants are often used as memorials, gifts and to mark special occasions such as births, deaths, weddings and holidays. Plants figure prominently in mythology, religion and literature. The field of ethnobotany studies plant use by indigenous cultures which helps to conserve endangered species as well as discover new medicinal plants. Gardening is the most popular leisure activity in the U.S. Working with plants or horticulture therapy is beneficial for rehabilitating people with disabilities. Certain plants contain psychotropic chemicals which are extracted and ingested, including tobacco, cannabis (marijuana), and opium.

Negative effects

Weeds are plants that grow where people do not want them. People have spread plants beyond their native ranges and some of these introduced plants become invasive, damaging existing ecosystems by displacing native species. Invasive plants cause billions of dollars in crop losses annually by displacing crop plants, they increase the cost of production and the use of chemical means to control them effects the environment.

Plants may cause harm to people. Plants that produce windblown pollen invoke allergic reactions in people who suffer from hay fever. A wide variety of plants are poisonous. Several plants cause skin irritations when touched, such as poison ivy. Certain plants contain psychotropic chemicals, which are extracted and ingested or smoked, including tobacco, cannabis (marijuana), cocaine and opium, causing damage to health or even death.[16][17] Both illegal and legal drugs derived from plants have negative effects on the economy, effecting worker productivity and law enforcement costs.[18][19] Some plants cause allergic reactions in people and animals when ingested, while other plants cause food intolerances that negatively effect health.

See also

References

1. ^ Haeckel G (1866). Generale Morphologie der Organismen. Berlin: Verlag von Georg Reimer, vol.1: i–xxxii, 1–574, pls I–II; vol. 2: i–clx, 1–462, pls I–VIII. 
2. ^ Van den Hoek, C., D. G. Mann, & H. M. Jahns, 1995. Algae:An Introduction to Phycology. pages 343, 350, 392, 413, 425, 439, & 448 (Cambridge: Cambridge University Press). ISBN 0-521-30419-9
3. ^ Van den Hoek, C., D. G. Mann, & H. M. Jahns, 1995. Algae:An Introduction to Phycology. pages 457, 463, & 476. (Cambridge: Cambridge University Press). ISBN 0-521-30419-9
4. ^ Crandall-Stotler, Barbara. & Stotler, Raymond E., 2000. "Morphology and classification of the Marchantiophyta". page 21 in A. Jonathan Shaw & Bernard Goffinet (Eds.), Bryophyte Biology. (Cambridge: Cambridge University Press). ISBN 0-521-66097-1
5. ^ Schuster, Rudolf M., The Hepaticae and Anthocerotae of North America, volume VI, pages 712-713. (Chicago: Field Museum of Natural History, 1992). ISBN 0-914-86821-7.
6. ^ Buck, William R. & Bernard Goffinet, 2000. "Morphology and classification of mosses", page 71 in A. Jonathan Shaw & Bernard Goffinet (Eds.), Bryophyte Biology. (Cambridge: Cambridge University Press). ISBN 0-521-66097-1
7. ^ Raven, Peter H., Ray F. Evert, & Susan E. Eichhorn, 2005. Biology of Plants, 7th edition. (New York: W. H. Freeman and Company). ISBN 0-7167-1007-2.
8. ^ Gifford, Ernest M. & Adriance S. Foster, 1988. Morphology and Evolution of Vascular Plants, 3rd edition, page 358. (New York: W. H. Freeman and Company). ISBN 0-7167-1946-0.
9. ^ Taylor, Thomas N. & Edith L. Taylor, 1993. The Biology and Evolution of Fossil Plants, page 636. (New Jersey: Prentice-Hall). ISBN 0-13-651589-4.
10. ^ lnternational Union for Conservation of Nature and Natural Resources, 2006. IUCN Red List of Threatened Species:Summary Statistics
11. ^ Kenrick, Paul & Peter R. Crane. 1997. The Origin and Early Diversification of Land Plants: A Cladistic Study. (Washington, D.C.: Smithsonian Institution Press). ISBN 1-56098-730-8.
12. ^ Smith, Alan R., Kathleen M. Pryer, E. Schuettpelz, P. Korall, H. Schneider, & Paul G. Wolf. (2006). "A classification for extant ferns". Taxon 55(3): 705-731.
13. ^ Robbins, W.W., Weier, T.E., et al, Botany:Plant Science, 3rd edition , Wiley International, New York, 1965.
14. ^ Goyal, K., Walton, L. J., & Tunnacliffe, A. (2005). LEA proteins prevent protein aggregation due to water stress. Biochemical Journal 388 (Part 1): 151 – 157. PMID 15631617. 
15. ^ Bromeliad Phytotelmata[1]
16. ^ cocaine/crack.
17. ^ Deaths related to cocaine.
18. ^ ILLEGAL DRUGS DRAIN $160 BILLION A YEAR FROM AMERICAN ECONOMY.
19. ^ The social cost of illegal drug consumption in Spain.

Further reading

General:
  • Evans, L. T. (1998). Feeding the Ten Billion - Plants and Population Growth. Cambridge University Press. Paperback, 247 pages. 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.: Smithsonian Institution Press. ISBN 1-56098-730-8.
  • Raven, Peter H., Evert, Ray F., & Eichhorn, Susan E. (2005). Biology of Plants (7th ed.). New York: W. H. Freeman and Company. ISBN 0-7167-1007-2.
  • Taylor, Thomas N. & Taylor, Edith L. (1993). The Biology and Evolution of Fossil Plants. Englewood Cliffs, NJ: Prentice Hall. ISBN 0-13-651589-4.
  • Trewavas, A. (2003). Aspects of Plant Intelligence, Annals of Botany 92: 1-20.
Species estimates and counts:
  • Prance, G. T. (2001). Discovering the Plant World. Taxon 50: 345-359.
  • International Union for Conservation of Nature and Natural Resources (IUCN) Species Survival Commission (2004). IUCN Red List of Threatened Species http://www.redlist.org.
  • Both the above are cited in Nature Conservancy, Spring 2006, p. 14.

External links

Botanical and vegetation databases


The Cambrian is a major division of the geologic timescale that begins about 542 ± 1.0 Ma (million years ago) at the end of the Proterozoic eon and ended about 488.3 ± 1.7 Ma with the beginning of the Ordovician period (ICS, 2004).
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Scientific classification or biological classification is a method by which biologists group and categorize species of organisms. Scientific classification also can be called scientific taxonomy, but should be distinguished from folk taxonomy, which lacks scientific basis.
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Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
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Archaeplastida
Adl et al. 2005

Phyla
  • Viridiplantae/Plantae
  • Chlorophyta
  • Charophyta
  • Embryophyta
  • Rhodophyta

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Ernst Haeckel

Born January 16 1834(1834--)

Died July 9 1919 (aged 85)

Nationality

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Green algae are microscopic protists; found in all aquatic environments, including marine, freshwater and brackish water.

The green algae (singular: green alga) are the large group of algae from which the embryophytes (higher plants) emerged.
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Chlorophyta
Reichenbach, 1834; Pascher[1][2]

Classes[3]
  • Bryopsidophyceae
  • Chlorophyceae
  • Pedinophyceae
  • Pleurastrophyceae
  • Prasinophyceae
  • Trebouxiophyceae
  • Ulvophyceae
Chlorophyta
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Charophyta

Classes

Mesostigmatophyceae
Chlorokybophyceae
Klebsormidiophyceae
Zygnemophyceae
   Zygnematales
   Desmidiales
Charophyceae
   Coleochaetales
   Charales

The
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Embryophyta

Divisions
  • Non-vascular land plants (bryophytes)
  • Marchantiophyta - liverworts
  • Anthocerotophyta - hornworts

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The bryophytes are those embryophytes ('land plants') that are non-vascular: they have tissues and enclosed reproductive systems, but they lack vascular tissue that circulates liquids. They neither flower nor produce seeds, reproducing via spores.
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Marchantiophyta
Stotler & Stotl.-Crand., 1977 emend. 2000

Classes and Orders

Haplomitriopsida Stotler & Stotl.-Crand.
  • Haplomitriales (Calobryales)
  • Treubiales
Jungermanniopsida Stotler & Stotl.-Crand.
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Anthocerotophyta

Class: Anthocerotopsida

Families & Genera

Leiosporocerotaceae
  • Leiosporoceros
Anthocerotaceae
  • Anthoceros
  • Folioceros

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MOSS may refer to:
  • Market Oriented Sector Selective talks, trade negotiations held between the United States and Japan in 1984
  • Microsoft Office SharePoint Server 2007, the current version of what used to be known as SharePoint Portal Server

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Divisions
  • Non-seed-bearing plants
  • †Rhyniophyta
  • †Zosterophyllophyta
  • Lycopodiophyta

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Rhyniophyta is a name sometimes used for the group of plants found in the Rhynie chert, Lagerstätte (rich fossil beds) in Aberdeenshire, Scotland. The Rhyniophyta or Rhynie flora are unusual for their excellent preservation of very early fossils of primitive vascular plants, in
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Lycopodiophyta

Classes

Lycopodiopsida - clubmosses
Selaginellopsida - spikemosses
Isoetopsida - quillworts and scale trees
† Zosterophyllopsida - zosterophylls

The Division Lycopodiophyta (sometimes called Lycophyta
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FERN

Charity
Founded 1995, The Netherlands
Headquarters Brussels, Belgium and Moreton-in-Marsh, UK

Key people Jutta Kill
Leontien Krul
Iola Leal Riesco
Judith Neyer
Saskia Ozinga
Industry Environmentalism
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Divisions
  • Pinophyta
  • Cycadophyta
  • Ginkgophyta
  • Gnetophyta
  • Magnoliophyta
The spermatophytes (from the Greek word "Σπερματόφυτα") (also known as phanerogams
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Pteridospermatophyta

Orders
  • Arberiales
  • Calamopityales
  • Callistophytales
  • Corystospermales
  • Gigantonomiales
  • Glossopteridales
  • Leptostrobales
  • Peltaspermales


"Pteridospermatophyta", also called seed ferns
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Pinophyta

Class: Pinopsida

Orders & Families

Cordaitales †
Pinales
  Pinaceae - Pine family
  Araucariaceae - Araucaria family
  Podocarpaceae - Yellow-wood family
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Cycadophyta

Class: Cycadopsida

Order: Cycadales
Dumortier

Families

Cycadaceae cycas family
Stangeriaceae stangeria family
Zamiaceae zamia family

Cycads
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Ginkgoaceae

Genus: Ginkgo

Species
G. biloba L.
The Ginkgo (Ginkgo biloba; '銀杏' in Chinese), frequently misspelled as "Gingko", and also known as the
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Gnetophyta

Class: Gnetopsida

Orders
  • Gnetales
  • Welwitschiales
  • Ephedrales


The plant division Gnetophyta
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Magnoliophyta

Classes

Magnoliopsida - Dicots
Liliopsida - Monocots

The flowering plants or angiosperms are the most widespread group of land plants. The flowering plants and the gymnosperms comprise the two extant groups of seed plants.
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Nematothallus
Lang 1937

Species
  • N. pseudo-vasculosa
Lang 1937
  • N.

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Life (Biota)

Domains and Kingdoms
  • Life on Earth (Gaeabionta)
  • Nanobes

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Plantae
  • Chromalveolata
  • Heterokontophyta
  • Haptophyta
  • Cryptophyta
  • Alveolata

  • ..... Click the link for more information.
  • tree is a perennial woody plant. It is sometimes defined as a woody plant that attains diameter of 10 cm (30 cm girth) or more at breast height (130 cm above ground).
    ..... Click the link for more information.
    Herbs (IPA: hə(ɹ)b, or əɹb; see pronunciation differences) are seed-bearing plants without woody stems, which die down to the ground after flowering.
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