The potato, Solanum tuberosum, is a widely grown and important staple food in temperate countries. It originated at high altitude in the Andes. The plant is grown from a tuber. The tuber produces "eyes", which are buds that grow out into vertical stems when the tuber is planted. These stems produce leaves above ground, and both roots and rhizomes ( underground stems ) below ground. During the growing season the tips of the rhizomes develop swollen ends that eventually produce the crop of harvestable tubers.The picture shows a small developing tuber (centre) at the tip of a rhizome. The rhizome is white and unbranched.Throughout the picture, the thinner branched strands visible are the roots of the plant, which absorb water and nutrients from the soil in order to maintain growth of the tubers. The tuber in the picture is approximately 1.5cm in diameter.