Wiktionary
n. (context botany English) A part of a plant, such as a bulb, specifically modified for storage of energy (generally in the form of carbohydrates) or of water.
Wikipedia
A storage organ is a part of a plant specifically modified for storage of energy (generally in the form of carbohydrates) 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 classification system. Storage organs often, but not always, act as perennating organs which enable plants to survive adverse conditions (such as cold, excessive heat, lack of light or drought).
Usage examples of "storage organ".
Not only his stomach but his new storage organ should be full of glucose and other readily metab.
Not only his stomach but his new storage organ should be full of glucose and other readily metabolized substances.
Not only his stomach but his new storage organ should be full of glucose and other readily metab-olized substances.
It's a defense thing, since from a distance the butt looks like the head, with dark spots for eyes and ears and mouth, but it's just a fat-and-water storage organ.