This means that they obtain their energy from sunlight, using chloroplasts derived from endosymbiosis with cyanobacteria to produce sugars from carbon dioxide and water, using the green pigment chlorophyll.

Historically, as in Aristotle's biology, the plant kingdom encompassed all living things that were not animals, and included algae and fungi.

A definition based on genomes includes the Viridiplantae, along with the red algae and the glaucophytes, in the clade Archaeplastida.

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

[15][17] Plants range in scale from single-celled organisms such as desmids (from 10 micrometres (μm) across) and picozoa (less than 3 μm across),[18][19] to the largest trees (megaflora) such as the conifer Sequoia sempervirens (up to 120 metres (380 ft) tall) and the angiosperm Eucalyptus regnans (up to 100 m (325 ft) tall).

[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.

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 secondary wood in trees such as Archaeopteris.

[39][40] The Carboniferous period saw the development of forests in swampy environments dominated by clubmosses and horsetails, including some as large as trees, and the appearance of early gymnosperms, the first seed plants.

[42] This may have set the scene for the evolution of flowering plants in the Triassic (~200 million years ago), with an adaptive radiation in the Cretaceous so rapid that Darwin called it an "abominable mystery".

Plant cells differentiate into multiple cell types, forming tissues such as the vascular tissue with specialized xylem and phloem of leaf veins and stems, and organs with different physiological functions such as roots to absorb water and minerals, stems for support and to transport water and synthesized molecules, leaves for photosynthesis, and flowers for reproduction.

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.

[61] Factors of the physical or abiotic environment include temperature, water, light, carbon dioxide, and nutrients in the soil.

The stamens create pollen, which produces male gametes that enter the ovule to fertilize the egg cell of the female gametophyte.

[81] 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% oxygen.

The fungal endophyte Neotyphodium coenophialum in tall fescue grass has pest status in the American cattle industry.

Hemiepiphytes like the strangler fig begin as epiphytes, but eventually set their own roots and overpower and kill their host.

[92] Among the epiphytes, the bromeliads accumulate water in their leaf axils; these water-filled cavities can support complex aquatic food webs.

Human cultivation of plants is the core of agriculture, which in turn has played a key role in the history of world civilizations.

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.

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

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

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

[113][114] The fossil fuels coal, petroleum and natural gas are derived from the remains of aquatic organisms including phytoplankton in geological time.

[118] Cloth is often made from cotton, flax, ramie or synthetic fibres such as rayon, derived from plant cellulose.

[134] Another widespread ancient motif, found for example in Iran, has a tree of life flanked by a pair of confronted animals.

[140] Some plants that produce windblown pollen, including grasses, invoke allergic reactions in people who suffer from hay fever.