Cytokinins are plant growth substances that primarily promote cell division. They can induce cell division in tissue culture experiments and the formation of interfascicular cambium. Cytokinins also delay senescence in leaves by reducing the breakdown of chlorophyll and proteins, help break bud dormancy, and counteract apical dominance by promoting growth of lateral buds.

1. CYTOKININS
Physiological Effects

2. What is Cytokinins………
 They are the plant growth substances
which act primarily on cell division and
have little or no effect on extension
growth.
 It is also known as Kinetin due to its
property to activate cell division
(cytokinesis)

3. Effects…….
 Cell Division:
 Most important function
 Varying amounts of cytokinins along with
auxins is required for growth of callus in
tissue culture experiments
 True cell division factors

4.  Cell enlargement:
 This effect occurs in absence of auxin
 Partly due to water uptake by cells and
partly due to increased plasticity of cells
 Tobacco pith culture and tobacco roots

5.  Initiation of Interfascicular Cambium:
 Kinetin can induce formation of interfasicular cambium.

6.  Morphogenesis:
 Auxin interaction controls the
morphogenetic differentiation of shoot
and root meristem
 Tobacco pith callus tissue grown in high
auxin & low cytokinin
 High cytokinin & low auxin promotes the
formation of shoot buds

7.  Counteraction of apical dominance:
 External application promotes growth of lateral
buds even if apical bud is intact
 Breaking dormancy

8.  Delay of senescence (Richmond-
Lang effect):
 Phenomenon in which mature leaves lose
chlorophyll, turn yellow, protein are
degraded and ultimately shed from plants
 Application of cytokinins delays senescence
for a no. of days
 Reduce breakdown of chlorophyll, proteins
and nucleic acids

9.  Accumulation & translocation of
solutes:
 Help solute translocation in phloem
 During development it helps phloem to carry
more nitrogen and other nutrients to the
required sites