Ppt with slideshare

1. 

2. 
`

3.  Cytokinins are plant hormones which regulate the plant growth.
 The name cytokinin is derived from its ability to induce cytokinesis
during cell divisions.
 Cytokinins have been found in all complex plants, as well as mosses,
fungi, and bacteria .
 Cytokinins were discovered by Skoog and his students .
Cytokinins

5. 
 Natural cytokinins
 Almost all naturally occurring cytokinins are the
products of purine nucleotide derivatives.
 The cytokinin zeatin is named after the genus of
corn,Zea, in which it was discovered.

6. 

7. 

8. 

9. 
Pith tissue were taken out from the stem of tobacco
plant and grow in culture medium . Auxins is
added in medium but do not divide and slightly
enlarge . Then add both auxins and kinetin were
together put in the medium Now the pith cells
starts dividing rapidly by mitosis.

10. 
 Senescense of leaves leads to yellowing and finally
leads to the fall from the plant.
 If such leaves are provided with cytokinin, the
yellowing is significantly delayed .

11. 
Isolated cotyledons of radish and other plants
expand dramatically when they are treated
with cytokinin.

12. 
Dormant buds that remain inactive for a
long time. If such buds are treated with
cytokinins they come out of dormant state.
 Effect on Dormancy

13. 
 The differentiation of different tissue like root ,
shoot from callus is called morphogenesis.
 The Cytokinin to auxin ratio is 10 : 1 .it produces
callus.

14.  Synthesized in the root tips, and then they are
translocated to different regions particularly to
meristematic and expanding tissues; transportation
is through xylem stream.

15. 

16. 
Biosynthesis
 Adenosine phosphate-isopentenyl transferase (IPT) catalyses the first reaction in
the biosynthesis of isoprene cytokinins. It may use ATP, ADP, or AMP as substrates and
may use dimethylallyl pyrophosphate (DMAPP) or hydroxymethylbutenyl
pyrophosphate (HMBPP) as prenyl donors. This reaction is the rate-limiting step in
cytokinin biosynthesis. DMADP and HMBDP used in cytokinin biosynthesis are produced
by the methylerythritol phosphate pathway (MEP).
 Cytokinins can also be produced by recycled tRNAs in plants and bacteria. tRNAs
with anticodons that start with a uridine and carrying an already-prenylated adenosine
adjacent to the anticodon release on degradation the adenosine as a
cytokinin.] The prenylation of these adenines is carried out by tRNA-
isopentenyltransferase .