Write a short note on Cytokinins.

(N/A) Cytokinins have specific effects on cytokinesis and were discovered as kinetin (a modified form of adenine,a purine) from autoclaved herring sperm $DNA$.
$\Rightarrow$ Kinetin does not occur naturally in plants.
$=$ The search for natural substances with cytokinin-like activities led to the isolation of zeatin from corn kernels and coconut milk.
- Since the discovery of zeatin,several naturally occurring cytokinins and some synthetic compounds with cell division-promoting activity have been identified.
$\rightarrow$ Natural cytokinins are synthesized in regions where rapid cell division occurs,for example,root apices,developing shoot buds,and young fruits.
- They help in the production of new leaves,chloroplasts in leaves,lateral shoot growth,and adventitious shoot formation.
$=$ Cytokinins help overcome apical dominance.
- They promote nutrient mobilization,which helps in the delay of leaf senescence.