Tubers are a type of enlarged structure 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.
The term originates from the Latin tuber, meaning "lump, bump, swelling".
Some writers define the term "tuber" to mean only structures derived from stems; others use the term for structures derived from stems or roots.
A stem tuber forms from thickened rhizomes or stolons. The top sides of the tuber produce shoots that grow into typical stems