Hint:It is the ascending part of the axis having branches, leaves, flowers, and fruits. This structure develops from the plumule of the embryo of a germinating seed.
Potato tuber is modified or the edible part of potato is stem. The stem is not always typically like what it is. They are modified to perform a variety of functions like storage of food, organs of penetration, etc. The various modifications of stems are tuber, bulb, corm, stolon, and rhizome. A tuber is a thickened part of a stem that grows underground. It has buds capable of producing a new plant by vegetative propagation. A tuber stores a large amount of edible starch which is used as food. Hence the edible part of the potato is the stem.
Apart from storage, reproduction is also a function of a tuber. Under natural conditions, In the autumn or winter, the connection between tuber and the main stem is lost resulting in the ground. In the following spring, they can then produce shoots from their buds.
The bulb is also a modified stem having leaf bases that function as food storage found in garlic, tulips, etc.
Stolon is horizontal modified stems that run below the soil surface found in gingers, strawberries, etc.
So, the correct answer is ‘Stem’.
Note:A modified stem is derived from the stem tissues which exist under the soil surface. Starch is commonly the stored food material in tubers. Other carbohydrates that can be present in tubers are inulin and fructose.