Plantae Plantae Plants most likely evolved more than 430 million years ago from multicellular green algae. Currently there are over 266,000 known species in the world. The plant kingdom differs from the others in several important ways. All plants are eukaryotic, multicellular, and contain a cell wall made of cellulose and other polysaccharides. The life cycle exhibits alternation of generations of diploid sporophytes and haploid gametophytes.
Sporophytes produce haploid spores through meiosis.
The gametes fuse to form the sporophyte, thus completing the life cycle.