Kids Research Express

Plant, any member of the plant kingdom, comprising about 260,000 known species of mosses , liverworts , ferns , herbaceous and woody plants, bushes, vines , trees , and various other forms that mantle the Earth and are also found in its waters. Plants range in size and complexity from small, nonvascular mosses, which depend on direct contact with surface water, to giant sequoia trees, the largest living organisms, which can draw water and minerals through their vascular systems to elevations of more than 100 m (330 ft). Only a tiny percentage of plant species are directly used by humans for food, shelter, fiber, and drugs. At the head of the list are rice , wheat , corn , legumes , cotton , conifers , and tobacco , on which whole economies and nations depend. Of even greater importance to humans are the indirect benefits reaped from the entire plant kingdom and its more than 1 billion years of carrying out photosynthesis . Plants have laid down the fossil fuels that provide power fo...

The many species of organisms in the plant kingdom are divided into several phyla, or divisions, totaling about 260,000 species. The bryophytes are a diverse assemblage of three phyla of nonvascular plants, with about 16,000 species, that includes the mosses, liverworts, and hornworts. Bryophytes lack a well-developed vascular system for the internal conduction of water and nutrients and have been called nonvascular plants. It takes two generations to complete the plant life cycle (Alternation of Generations). The familiar leafy plant of bryophytes is the sexual, or gamete-producing, generation of the life cycle of these organisms. Because of the lack of a vascular system and because the gametes require a film of water for dispersal, bryophytes are generally small plants that tend to occur in moist conditions, although some attain large size under favorable circumstances and others (usually very small) are adapted to desert life. The other phyla are collectively termed vascular plan...