All organism of the kingdom Plantae are multicellular eukaryotic life forms characterized by photosynthetic nutrition, which is a characteristic possessed by all plants. Except, however, some parasitic plants and underground orchids, in which chemical energy is produced from water, minerals, and carbon dioxide with the aid of pigments and the radiant energy of the Sun. There is essentially unlimited growth at localized regions, cells that contain cellulose in their walls and are therefore to some extent rigid. There is an absence of organs of locomotion, resulting in a more or less stationary existence, and an absence of nervous systems.