Tubers develop by the swelling of tip of a special underground branch or stem that arise from axil of leaf. It accumulates a considerable amount of reserve food especially starch as in potato. Internally, the potato tuber is composed of narrow parenchymatous cells and angular collenchyma (thickened at corners) rich in starch.
Potato is highly nutritious and contains carbohydrate (22%), protein (2%), fats (0.1%) and water 74%. It is also rich in folic acid, pantothenic acid, pyridoxine, vitamin-C, iron (8−10%), thiamine and riboflavin.