F1 has nine subunits of five different types, with the composition α₃ β₃ ϒδε

TLS Online TPP Program

#Id: 4587

#Unit 6. System Physiology – Plant

Developmental changes by light (photomorphogenesis) transformation from the etiolated to the green state.

a. A decrease in the rate of stem elongation

b. The beginning of apical-hook straightening

c. The initiation of the synthesis of pigments

TLS Online TPP Program

#Id: 4638

#Unit 6. System Physiology – Plant

Seedlings grown in the dark display an etiolated growth pattern:

a) yellow unexpanded cotyledons

b) apical hook

c) Long hypocotyl

TLS Online TPP Program

#Id: 4947

#Unit 6. System Physiology – Plant

Expression of the other phytochrome types (B to E in angiosperms) is independent of light and both Pr and Pfr forms are stable.

TLS Online TPP Program

#Id: 4948

#Unit 6. System Physiology – Plant

Phytochrome B (PhyB) is probably the photoreceptor involved in shade detection and avoidance. This response allows many species to greatly increase their stem extension rate when they become shaded by competitors.

TLS Online TPP Program

#Id: 4949

#Unit 6. System Physiology – Plant

PHY genes encode two types of phytochrome

TLS Online TPP Program

#Id: 4950

#Unit 6. System Physiology – Plant

PHYA is the only gene that encodes a Type I phytochrome. Phytochrome A predominantly perceives far-red light.