The relationships between plant groups are still being worked out, and the names given to them vary considerably. Plants in a strict sense include the green algae, and land plants that emerged within them, including stoneworts. Green plants, also known as Viridiplantae, Viridiphyta, Chlorobionta or Chloroplastida 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 ). From least to most inclusive, these four groupings are: When the name Plantae or plant is applied to a specific group of organisms or taxon, it usually refers to one of four concepts. 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. However, these organisms are still sometimes considered plants, particularly in informal contexts. 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. 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).

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. The scientific study of plants is known as botany, a branch of biology.Īll living things were traditionally placed into one of two groups, plants and animals. 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. Plants that produce grain, fruit, and vegetables also form basic human foods and have been domesticated for millennia. Green plants provide a substantial proportion of the world's molecular oxygen, and are the basis of most of Earth's ecosystems.

There are about 320,000 known species of plants, of which the great majority, some 260–290 thousand, produce seeds. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is also common. 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. Their chloroplasts contain chlorophylls a and b, which gives them their green color. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria. The latter includes the flowering plants, conifers and other gymnosperms, ferns and their allies, hornworts, liverworts, and mosses.

By one definition, plants form the clade Viridiplantae (Latin name for 'green plants') which is sister of the Glaucophyta, and consists of the green algae and Embryophyta (land plants). Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi however, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes (the archaea and bacteria). Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae.

Green aesthetic