What do bulbs primarily consist of?

Bulbs primarily consist of short, underground stems that are covered by fleshy leaf bases. This structure allows bulbs to serve as storage organs, where they accumulate nutrients and energy in the form of carbohydrates. The fleshy leaf bases are modified leaves that can store water and nutrients, enabling the plant to survive adverse conditions such as drought or winter. During the growing season, a bulb will develop shoots and roots to facilitate growth and flowering, drawing on the stored resources.

The other options describe different parts of the plant that do not accurately represent the structure of a bulb. For instance, roots are essential for nutrient absorption but do not characterize the bulb itself, which is primarily the swollen storage structure. Aerial stems typically refer to above-ground growth that produces flowers but do not include the underground storage function of bulbs. Leaf structures that store water are more indicative of succulents rather than bulbs, which rely on their unique structure for both nutrient storage and the initiation of new growth cycles.