A storage organ's 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're better protected from attack by herbivores. Underground storage organs and the plants that bear them are sometimes called geophytes. In common parlance, underground storage organs may be generically called roots, tubers, or bulbs, but to the botanist there's more specific technical nomenclature: True roots: Tuber… (More on Geophyte)