What Happens to Phytochromes After Several Days of Dark, Rainy

Question

What happens to phytochromes after several days of dark, rainy weather?
A) Pr absorbs darkness and converts to Pfr.
B) Pr stimulates flowering.
C) Pr and Pfr become unstable and both are destroyed.
D) Pr and Pfr are both formed from inactive phytochrome.
E) Pfr spontaneously reverts to Pr.

Accepted Answer

Phytochromes exist in two forms: Pr and Pfr. In the absence of light, Pfr slowly reverts to Pr, which is the inactive form. During dark, rainy weather, the lack of light causes Pfr to convert back to Pr.