Question

What will be the effect on phytochrome in a plant subjected to continuous red light?

• A. Phytochrome synthesis will increase
• B. Level of phytochrome will decrease
• C. Phytochrome will be destroyed
• D. First (b) then (a)

Answer 1

The correct option is D First (b) then (a)

Phytochrome is a photodetector pigment in the plant. It is sensitive to the red and far-red region of the visible spectrum. It regulates the flowering. At 670 nm of light, it changes to Pfr and at 730 nm of light it changes to Pr.

If, we subject a plant to continuous red light, the level of phytochrome in the plant decrease below a critical value and triggers the de novo synthesis of more phytochromes in the Pr form. The result is an equilibrium in the plant between the synthesis and the destruction of phytochrome.

So, the correct answer is option D.