Final answer:
A potato stores its reserve of energy in its underground tuber in the form of starch. The tuber contains amyloplasts, which provide the necessary energy for the plant's growth.
Step-by-step explanation:
A potato stores its reserve of energy in its underground tuber in the form of starch. The tuber is a specialized structure that contains numerous starch-storing plastids called amyloplasts. These amyloplasts provide the energy and material needed for the potato plant to grow when favorable conditions return.