Phylogenetic relationships among species in a radiation are difficult to determine for two related reasons.                                                                 

a. During the short time between two successive speciation events, few new mutations are fixed.                                                                               

b. Incomplete lineage sorting may occur during rapid diversification.

TLS Online TPP Program

#Id: 10217

#Unit 6. System Physiology – Plant

Auxin and cytokinin are both required for the initiation of xylogenesis

TLS Online TPP Program

#Id: 10218

#Unit 6. System Physiology – Plant

KNOX transcription factors activate the cytokinin biosynthetic gene ISOPENTENYL TRANSFERASE7 -IPT7

TLS Online TPP Program

#Id: 10219

#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: 10220

#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.

TLS Online TPP Program

#Id: 10221

#Unit 6. System Physiology – Plant

KNOX gene expression increases cytokinin levels in the shoot apical meristem by upregulating the cytokinin biosynthetic gene ISOPENTENYL TRANSFERASE7 (IPT7)

TLS Online TPP Program

#Id: 10222

#Unit 6. System Physiology – Plant

Cytokinin maintains meristem by controlling cell division

 Deficient mutants – lonely guy (LOG)/STM

 Gene activates cytokinins