Question

Choose the correct answer from the alternatives given.
Light of wavelengths causes phytochrome to switch from inactive to active form whereas light of wavelengths has the opposite effect.

• A. red; far-red
• B. far-red; red
• C. red; blue
• D. far-red; blue

Answer 1

The correct option is A red; far-red

Phytochrome is receptors of light which are a blue-green pigment and are dependent upon red and far-red light for the process of flowering. The phytochromes are present in two forms:

1. Active form (Pfr)
2. Inactive form (Pr)

When the plants are exposed to a red light then phytochromes get activated (Pfr) and the help in the growth of the plant then later when exposed to a far-red light it gets deactivated and becomes inactive form (Pr) thus resulting in the stoppage of flowering.

So, the correct option is 'Red; far-red'.