As RNA polymerase moves along the DNA template, it unwinds the duplex at the front of the bubble (the unwinding point), and the DNA  automatically reforms the double helix at the back (the rewinding point).  The length of thetranscription bubble is 12 to 14 bp, but the length of the RNA–DNA hybrid within the bubble is only 8 to 9 bp. As the enzyme moves along the template, the DNA duplex reforms, and the RNA is displaced as a free polynucleotide chain The last 14 ribonucleotides in the growing RNA are complexed with the DNA and/or the enzyme at any given moment.

TLS Online TPP Program

#Id: 7533

#Unit 6. System Physiology – Plant

Dense plastids serve as gravity sensors

Gravity does not form gradient.

The only way of sensing gravity is through the motion of a sedimenting body.

In plants intracellular gravity sensors are large, dense amyloplast.

Statoliths –amyloplasts that function as gravity sensors.

Statocytes-specialized gravity sensing cells in which statoliths are present.

TLS Online TPP Program

#Id: 7534

#Unit 6. System Physiology – Plant

Strigolactones as signal that interact with auxin in regulating apical dominance Strigolactone is a group of trepenoids that produced in both shoots and roots and is transported through xylem

TLS Online TPP Program

#Id: 7535

#Unit 6. System Physiology – Plant

GA levels in plants are correlated with stem length, internode elongation and seed germination. Play role in seed germination, transition to flowering, and pollen development.

TLS Online TPP Program

#Id: 7536

#Unit 6. System Physiology – Plant

The biosynthesis of gibberellins is under strict genetic, developmental, and environmental control, and numerous gibberellin-deficient mutants have been isolated.  Mendel’s tall/dwarf alleles in peas are a famous example. Such mutants have been useful in elucidating the complex pathways of gibberellin biosynthesis.

TLS Online TPP Program

#Id: 7537

#Unit 6. System Physiology – Plant

Gibberellins Promote Seed Germination

TLS Online TPP Program

#Id: 7538

#Unit 6. System Physiology – Plant

Gibberellins are synthesized via the terpenoid pathway in three stages in Apical Tissues