The pseudobulb is a

storage organ 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 ...

found in many epiphytic and terrestrial

sympodial Sympodial growth is a bifurcating branching pattern where one branch develops more strongly than the other, resulting in the stronger branches forming the primary shoot and the weaker branches appearing laterally. A sympodium, also referred to a ...

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Along with the Asteraceae, they are one of the two largest families of floweri ...

s. It is derived from a thickening of the part of a stem between leaf nodes and may be composed of just one internode or several, termed heteroblastic and homoblastic respectively. All leaves and

inflorescence An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the modified part of the shoot of seed plants where flowers are forme ...

s usually arise from this structure. Pseudobulbs formed from a single internode produce the leaves and inflorescence from the top, while those that are formed from several internodes can possess leaves along its length.Hew, C.S., and J.W.H. Yong. 2004
The Physiology of Tropical Orchids in Relation to the Industry.
Singapore: World Scientific Publishing Co. pp. 13-15. The modified sheath leaves that appear at the base of a pseudobulb and often enfold all or part of it are usually dry and papery, though in some orchids the sheaths bear leaf blades and the leaves at the pseudobulb's apex are reduced to scales.Dressler, R.L. 1993. Phylogeny and Classification of the Orchid Family. Portland, Oregon: Dioscorides Press. p. 19. In some species, it is hardly swollen at all and looks like a normal stem with many leaves while at the other extreme, some genera such as ''

Bulbophyllum ''Bulbophyllum'' is a genus of mostly epiphytic and lithophytic orchids in the family Orchidaceae. It is the largest genus in the orchid family and one of the largest genera of flowering plants with more than 2,000 species, exceeded in number o ...

'' have single, spherical pseudobulbs with one (or two) leaves at the apex of each. Whether cane-like (with many joints) or spherical (with one or few joints), they are all produced from a long-lived creeping stem called a

rhizome In botany and dendrology, a rhizome (; , ) is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from axillary buds and grow ...

which may itself be climbing or pendulous. The pseudobulbs are relatively short lived (1–5 years), but are continually produced from the growing tip of the rhizome and may persist for years after its last leaves senesce. The term pseudobulb is used to distinguish the above-ground storage organ from other storage organs derived from stems that were underground, namely

corm A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ' ...

s or true

bulb In botany, a bulb is structurally a short stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs dur ...

s, a combination of an underground stem and storage leaves. Strictly speaking, there is no clear distinction between the pseudobulb and corm structures.

References

External links

*{{Commons-inline, Pseudobulbus (Orchidaceae), Pseudobulb Orchid morphology