Tuber

Tubers are enlarged structures used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing season, and as a means of asexual reproduction. Stem tubers form thickened rhizomes (underground stems) or stolons (horizontal connections between organisms); well known species with stem tubers include the potato and yam. Some writers also treat modified lateral roots (root tubers) under the definition; these are found in sweet potatoes, cassava, and dahlias.