What characteristic do tubers possess?

Tubers are specialized structures of certain plants that serve primarily as storage organs, allowing the plant to store energy. This energy is mainly in the form of carbohydrates, which are crucial for the plant's growth and survival during periods when conditions are not favorable for growth.

The ability to store energy underground allows tubers to remain protected from environmental extremes and allows the plant to access this stored energy when needed, particularly in the next growing season. This characteristic is what distinguishes tubers from other plant structures like roots, stems, or leaves.

The other options do not correctly describe the primary function or nature of tubers. For example, many tubers grow underground, not above ground, and while some tubers can have a high water content, this is not their defining characteristic. Furthermore, while some tubers may have a sweet taste (like sweet potatoes), not all are primarily sweet. Thus, the defining feature of tubers is their ability to store energy underground.