AskDefine | Define cytokinin

Dictionary Definition

cytokinin n : any of a class of plant hormones that promote cell division and delay the senescence of leaves [syn: kinin]

User Contributed Dictionary



  1. Any of a class of plant hormones involved in cell growth and division

Extensive Definition

right|122px|The cytokinin zeatin is named after the genus of corn, [[Teosinte|Zea, in which it was first discovered.]]
Cytokinins (CK) are a class of plant growth substances (plant hormones) active in promoting cell division, and are also involved in cell growth, differentiation, and other physiological processes. Their effects were first discovered through the use of coconut milk in the 1940s by a scientist at the University of Wisconsin-Madison named Folke Skoog.
There are two kinds of cytokinins, adenine-type cytokinins including kinetin, zeatin and 6-benzylaminopurine and phenylurea-type cytokinins like diphenylurea or thidiazuron (TDZ). There is no evidence that any phenylurea cytokinins occur naturally in plant tissues. Adenine-type cytokinins are synthesised in stems, leaves and roots, but the root is the major site; furthermore cambium and possibly all actively dividing tissues are responsible for the synthesis of this group of plant hormones. Cytokinin is involved in both local and long distance signalling; as a long distance signal CK shares the same transport systems used by the plant for moving purines and nucleosides.
Cytokinins are involved in many plant processes, including cell division, shoot and root morphogenesis, chloroplast maturation, cell enlargement, auxiliary bud release and senescence. The ratio of auxin to cytokinin is crucial during cell division and the differentiation of plant tissues and auxin is known to regulate the biosynthesis of cytokinin.
cytokinin in Czech: Cytokinin
cytokinin in German: Cytokinin
cytokinin in Spanish: Citoquinina
cytokinin in Finnish: Sytokiniini
cytokinin in French: Cytokinine
cytokinin in Hebrew: ציטוקינין
cytokinin in Dutch: Cytokinine
cytokinin in Japanese: サイトカイニン
cytokinin in Polish: Cytokininy
cytokinin in Turkish: Sitokinin
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