What is a tuber?

A tuber is defined as a fleshy, oblong or rounded thickening of a subterranean stem or shoot. This biological structure serves as a storage organ for nutrients, allowing plants to survive adverse conditions, such as winter or drought. Tubers, like potatoes, store carbohydrates and can produce new plants from their "eyes," which are growth buds. Understanding tubers is important in horticulture and agriculture, as they play a crucial role in plant propagation and nutrition.

The other options do not accurately define what a tuber is. A type of poisonous plant does not embody the characteristics of a tuber. Similarly, a form of pest that lives underground refers to organisms that can damage plants rather than being a part of their growth structure. Lastly, a classification of pesticide pertains to chemical substances used to manage pests and does not relate to the biological structure of a tuber. Therefore, option B accurately captures the essence of what a tuber is in the context of plant biology.