(ii) Synthetic Cytokinin:

Kinetin is also known as synthetic cytokinin.

Figure 8: Kinetin

Function of Cytokinin:
Stimulates cell division: Especially by controlling the transition from G2 mitosis. This effect is moderated by cyclin-dependent protein kinases (CDK's) and cyclins. Stimulates morphogenesis (shoot initiation/bud formation) in tissue culture: In plant tissue cultures, cytokinin is required for the growth of a callus. Stimulates the growth of lateral buds- Cytokinin application to dormant buds causes them to develop. Witches' broom is caused by a pathogen Corynebacterium fascians (or Agrobacterium tumefaciens) that produces cytokinin which, in turn, stimulates lateral bud development. Thus apical dominance may be related to cytokinin too. Stimulates leaf expansion resulting from cell enlargement: Cytokinins stimulate the expansion of cotyledons. The mechanism is associated with increased plasticity of the cell wall. May enhance stomatal opening in some species. Promotes the conversion of etioplasts into chloroplasts via stimulation of chlorophyll synthesis.