A G protein– coupled receptor kinase phosphorylates serine and threonine residues in the

cytoplasmic segments of activated GPCRs

TLS Online TPP Program

#Id: 4982

#Unit 6. System Physiology – Plant

HIR action spectrum for the inhibition of hypocotyl elongation of dark-grown lettuce seedlings. The peaks of activity for the inhibition of hypocotyl elongation occur in the UV-A, blue, and far-red regions of the spectrum.

TLS Online TPP Program

#Id: 4983

#Unit 6. System Physiology – Plant

Role of phytochrome in shade perception in sun plants versus shade plants.

TLS Online TPP Program

#Id: 4985

#Unit 6. System Physiology – Plant

The ratio of red light (R) to far-red light (FR) varies remarkably in different environments. This ratio can be defined as follows:

TLS Online TPP Program

#Id: 4986

#Unit 6. System Physiology – Plant

Phytochrome is that it enables plants to sense shading by other plants. Plants that increase stem extension in response to shading are said to exhibit a shade avoidance response.

TLS Online TPP Program

#Id: 4988

#Unit 6. System Physiology – Plant

As shading increases, the R:FR ratio decreases.

TLS Online TPP Program

#Id: 4989

#Unit 6. System Physiology – Plant

The greater proportion of far-red light converts more Pfr to Pr, and the ratio of Pfr to total phytochrome (Pfr/Ptotal) decreases.