Theory:

Cytokinins were discovered by F. Skoog, C. Miller and co-workers during the \(1950s\) as factors that promote cell division (cytokinesis) in plant cells. It was first isolated from Zea mays (known as Zeatin) and is abundantly found in the liquid endosperm of coconuts.
They are naturally occurring growth promoters that combine with auxin, promote cell division and differentiation in plants.
800px-Zeatin.png
Cytokinin (Zeatin)
Physiological effects of cytokinin:
  • These are the substances that induce cell division (cytokinesis) in the presence of auxins.
512px-Cytokinesis_illustration.svg.png
Cytokinesis
  • These substances also cause the enlargement of cells.
  • Together with auxins, cytokinins are involved in morphogenesis.
The formation of tissue culture from the callus in tissue culture is known as morphogenesis.
  • They also promote the growth of lateral buds even in the presence of apical buds.
Apical_Cycle.gif
Apical bud and lateral bud
  • Application of cytokinins promotes the Richmond Lang effect, i.e., it delays ageing in plants.
Reference:
https://commons.wikimedia.org/wiki/File:Zeatin.png
https://commons.wikimedia.org/wiki/File:Cytokinesis_illustration.svg
https://upload.wikimedia.org/wikipedia/commons/7/7b/Apical_Cycle.gif