All About Plants by Inamdar Habiba Plants Plants Structure Word to know Plants Development Plants disease How Do Plants Help the Environment Plants A plant is any organism in the kingdom Plantae. Kingdoms are the main divisions into which scientists classify all living things on Earth . The other kingdoms are: Monera (single-celled organisms without nuclei), Protista (single-celled organisms with a nucleus), Fungi, and Animalia (animals). The scientific study of plants is called botany. A general definition of a plant is any organism that contains chlorophyll (a green pigment contained in a specialized cell called a chloroplast) and can manufacture its own food. Another characteristic of plants is that their rigid cell walls are composed mainly of cellulose, a complex carbohydrate that is insoluble (cannot be dissolved) in water. Because of the vast number of plants that exist, cellulose is the m...