Nucleation phase 

Lag period (Time taken for nucleation) Rate-limiting Step.

TLS Online TPP Program

#Id: 7562

#Unit 6. System Physiology – Plant

Cytokinin has been linked to the activation of a Cdc25- like phosphatase, whose role is to remove an inhibitory phosphate group from the Cdc2 kinase.  Cytokinins elevate the expression of the CYCD3 gene, which encodes a D-type cyclin

TLS Online TPP Program

#Id: 7563

#Unit 6. System Physiology – Plant

Cytokinin binds to the CRE1 receptors to initiate a response that culminates in the elevation of transcription of the type- BARRs/ type- A ARRs. 

TLS Online TPP Program

#Id: 7564

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7565

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7566

#Unit 6. System Physiology – Plant

The isopentenyltransferase gene (IPT) that encodes a rate limiting enzyme in cytokinin biosynthesis, under the control of a water-deficit responsive and maturation specific promoter PSARK was introduced into cotton and the performance of the PSARK::IPT transgenic cotton plants was analyzed in the greenhouse and growth chamber conditions. 

The data indicate that PSARK::IPT-transgenic cotton plants displayed delayed senescence under water deficit conditions in the greenhouse. 

TLS Online TPP Program

#Id: 7567

#Unit 6. System Physiology – Plant

PSARK::IPT transgenic cotton plants produced more root and shoot biomass, dropped fewer flowers, maintained higher chlorophyll content, and higher photosynthetic rates under reduced irrigation conditions in comparison to wild-type and segregated non-transgenic lines. 

Furthermore, PSARK::IPT-transgenic cotton plants grown in growth chamber condition also displayed greater drought tolerance.  These results indicate that water-deficit induced expression of an isopentenyltransferase gene in cotton could significantly improve drought tolerance.