Here's why:

* True Roots: True roots grow downwards from the base of a plant and anchor it to the soil. They also absorb water and nutrients.

* Stems: Stems are the supporting structures of a plant that hold leaves, flowers, and fruits. They can grow above or below ground.

While potatoes grow underground, they don't have the characteristics of true roots. They have nodes, buds (called eyes), and internodes, which are typical features of stems. The "potato" we eat is actually a modified stem called a tuber, which stores starch as food for the plant.