A bulb is a short stem with fleshy leaves

Leaf

A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....

 or leaf bases. The leaves often function as food

Food

Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

 storage organ

Storage organ

A storage organ is a part of a plant specifically modified for storage of energy or water. Storage organs often grow underground, where they are better protected from attack by herbivores. Plants that have an underground storage organ are called geophytes in the Raunkiær plant life-form...

s during dormancy

Dormancy

Dormancy is a period in an organism's life cycle when growth, development, and physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be closely associated with environmental conditions...

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A bulb's leaf bases, known as scales, generally do not support leaves, but contain food reserves to enable the plant to survive adverse conditions. At the center of the bulb is a vegetative growing point or an unexpanded flowering shoot. The base is formed by a stem

Plant stem

A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...

, and plant growth occurs from this basal plate.