The physiological effects of cytokinins are
Cell division: Induction of cell division is considered as a major function of cytokinins in plants.
Cell expansion: In Soya bean leaf discs and radish cotyledons, the addition of cytokinins results in a remarkable increase in size due to cell elongation.
Organ formation or Morphogenesis: Cytokinins in association with auxins, induce differentiation of organs. Skoog and his associates found that if a higher cytokinin to auxin ratio is maintained in the culture media, tissue differentiation takes place resulting in the formation of buds, stems, and leaves. On the other hand a low ratio of cytokinin favours root formation.
Delay in senescence or Richmond – Land effect: The ability of cytokinin to delay the process of senescence in plants is called Richmond-Lang effect. Senescence in leaves is maintained by yellowing.It is due to the breakdown or decreased synthesis of chlorophylls, RNA and proteins. Senescence is followed by the death of organs or whole plant. If a proper concentration of cytokinins are applied to the plants, plants remain green and healthy.
Opening of stomata: Cytokinins increase the potassium ion concentration in guard cells and help in the opening of stomata.