Cytokinin - Chemical structure, Physiological function and uses

 

The cytokinin is a basic hormone being derivative of either amino purine or phenyl urea that promote cytokinesis.

Cytokinin is a plant hormone that is responsible for the  growth and the stimulation of cell division. Cytokinins are synthesised in the roots and are a derivative of  adenine.it  moves upward and passes into the leaves and fruits, where they are required for normal growth and cell differentiation.

F. Skoog and his co-workers observe that from the inter nodal segment of tobacco stem callus proliferate  only if in addition to Auxin  the nutrient medium was supplemented with extract of yeast  vascular tissue and  coconut milk or  DNA. 

The first cytokinin was discovered by Miller from degraded autoclaved herring sperm DNA. It is called Kinetin and does not occur naturally in plants. The first natural cytokinin in plants was obtained from unripe maize grain  called zeatin. It is 4 hydroxy 3 methyl cis 2 butenyl amino purine. It is also found in coconut milk. 

It is mainly found in regions  where Rapid cell division occurs, that is root Apices  developing Shoot  bud young fruit etc. 

Tobacco pith culture, retardation of leaf senescence and excised radish cotyledon expansion are used as bioassay for cytokinin. 

Cell division activity is enhanced by cytokinin. Cytokinin controls initiation of plant organs like morphogenesis. Cytokinin increases the growth of Seedling in width. Cytokinin help overcome the apical dominance it helps in induction of the femaleness in male plant and retards senescence. This is called the Richmond lang effect.

Mobilisation of food material is increased by the application of cytokinin.The application of cytokinin to market vegetables can keep them fresh for several days.