Overdominance the heterozygote has higher fitness than the  fitnesses of the two homozygotes

Underdominance, in which the heterozygote has lower fitness than both homozygotes.

Directional selection leads to fixation of the favored allele and elimination of the other allele, as  long as no other evolutionary forces act on the population.

TLS Online TPP Program

#Id: 10218

#Unit 6. System Physiology – Plant

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

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#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. 

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#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)

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#Id: 10222

#Unit 6. System Physiology – Plant

Cytokinin maintains meristem by controlling cell division

 Deficient mutants – lonely guy (LOG)/STM

 Gene activates cytokinins

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#Id: 10223

#Unit 6. System Physiology – Plant

Organo-genesis