Cytokinins or kinetins was discovered by Miller et al .in 1955 . It plays a key role in the life of higher plants . It induces cell division in plants and thus , influence plant growth by promoting cell division. According to skoog and his co-workers (1964)and mothes (1967) in general , " the term cytokinins is universally used as generic name for substance which promotes cell division and exerts other growth regulatory functions . "
STRUCTURE AND DISTRIBUTION
Cytokinins are synthesized in the cell dividing region . They are also found in actively growing region like fruits ,seeds and embryos. In the mature plants , they are found in roots from where they are transported to leaves.
ROLE AND APPLICATION OF CYTOKININS
Cell division :- The most important function of cytokinins is to induce cell division in plants. It promotes cell division especially in the presence of auxins.
Cell enlargement:- Cytokinins can cause the enlargement of cells in leaf , cotyledons and tobacco pith .
Promotes organ differentiation in callus :- Cytokinins plays an important role in the initiation of plant organ in callus . High cytokinins / auxin ratio induces - shoot formation , Low cytokinins / auxin ratio induces - root formation. , Moderate cytokinins / auxin ratios - root and shoot development , Moderate cytokinins / less auxin ratio induces - active mitosis division
Dormancy :- Cytokinins are quite effective in breaking the dormancy of seeds and some other plant organs .
Counteraction of apical dominance :- Application of cytokinins promotes the growth of lateral buds even in the presence of the apical bud . Thus , the cytokinins reverse the trend feet of auxins and counteracts the apical dominance.
Protein synthesis :- Cytokinins increases the rate of protein synthesis.
Delay of senescence:- As the leaves grow older , they turn yellow and ultimately fall off from the plants . This is called senescence . Application of cytokinins delay senescence.
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