Bald Cypress Taxodium distichum Knees High DoF

A cypress knee is a distinctive structure forming above the roots of a cypress

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

of any of various species of the subfamily

Taxodioideae Taxodioideae is a subfamily in Cupressaceae Cupressaceae is a conifer family, the cypress family, with worldwide distribution. The family includes 27–30 genera (17 monotypic), which include the junipers and redwoods, with about 130–140 sp ...

, such as the

bald cypress ''Taxodium distichum'' (bald cypress, swamp cypress; french: cyprès chauve; ''cipre'' in Louisiana) is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to a wide ...

. Their function is unknown, but they are generally seen on trees growing in swamps. Some current hypotheses state that they might help to aerate the tree's roots, create a barrier to catch sediment and reduce erosion, assist in anchoring the tree in the soft and muddy soil, or any combination thereof. Knees are

wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin ...

y projections sent above the normal water level, roughly vertically from the

root In vascular plants, the roots are the organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often below the su ...

s, with a near-right-angle bend taking them vertically upward through water. One early assumption of their function was that they provided oxygen to the roots that grow in the low dissolved

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

(DO) waters typical of a swamp, acting as

pneumatophores Aerial roots are roots above the ground. They are almost always adventitious. They are found in diverse plant species, including epiphytes such as orchids (''Orchidaceae''), tropical coastal swamp trees such as mangroves, banyan figs (''Fic ...

mangrove A mangrove is a shrub or tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves are taxonomically diverse, as a result of convergent evolution in severa ...

s have similar adaptations. There is little actual evidence for this assertion; in fact, swamp-dwelling specimens whose knees are removed continue to thrive, and laboratory tests demonstrate that the knees are not effective at depleting oxygen in a sealed chamber. Even though there is no expert consensus on their role, the supposition that they are pneumatophores is repeated without comment in several introductory botany textbooks. Another more likely function is that of structural

buttress A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall. Buttresses are fairly common on more ancient buildings, as a means of providing support to act against the lateral ( ...

ed support and stabilization. Lowland or swamp-grown cypresses found in flooded or flood-prone areas tend to be buttressed and "kneed," as opposed to cypresses grown on higher ground, which may grow with very little taper. Trees that develop these "knees" include: * ''

Glyptostrobus ''Glyptostrobus'' is a small genus of conifers in the family Cupressaceae (formerly in the family Taxodiaceae). The sole living species, '' Glyptostrobus pensilis'', is native to subtropical southeastern China, from Fujian west to southeast Yu ...

'' *

Bald cypress ''Taxodium distichum'' (bald cypress, swamp cypress; french: cyprès chauve; ''cipre'' in Louisiana) is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to a wide ...

* Pond cypress * Ahuehuete *

Metasequoia ''Metasequoia'', or dawn redwoods, is a genus of fast-growing deciduous trees, one of three species of conifers known as redwoods. The living species '' Metasequoia glyptostroboides'' is native to Lichuan county in Hubei province, China. Althou ...

References

External links

*Christopher H. Briand.
Cypress Knees: An Enduring Enigma
" Arnoldia. 2000-2001.Vol. 60(4). p. 19-20, 21-25. An extensive review of the published literature concerning cypress knees. {{DEFAULTSORT:Cypress Knee Cupressaceae Plant roots

See also

References

External links