The New Student's Reference Work/Digestion

Diges′tion in plants is essentially the same process as in animals. It consists in producing such chemical changes in insoluble foods that they become soluble in water, and consequently fit for absorption or transfer; or, when already soluble, in reducing them to simpler forms. There are no special digestive organs in plants comparable to the alimentary canal of animals, with its connected glands; and likening the leaves to the stomach is misleading. Digestion is usually accomplished by the action of enzymes (which see) or ferments secreted by the living protoplasm. (See Secretion.) In some cases these enzymes are produced in special glands; in others they are formed by the same cells that have other functions. Digestion often occurs outside the plant-body as when the embryo secretes diastase (see Enzymes) to digest the starch stored around it; or when a fungus digests the cellulose of a cell-wall which it is penetrating. Or digestion may occur within the plant-body, as when the starch stored in a potato-tuber is digested in order to be transferred to the growing regions, or the starch-granules formed in a leaf are digested to be carried away to places of use or storage.