Question

The inhibitory effect of red light on flowering during critical dark period in short day plants can be overcome by

• A. Blue light
• B. Far-red light
• C. Infra-red rays
• D. Ultraviolet rays

Answer 1

The correct option is B Far-red light

Short day plants require the long duration of the dark period. If the dark period is interrupted with a brief exposure to red light (660 nm), the flowering will not take place. The inhibitory effect of red light on flowering during the critical dark period in short day plants can be overcome by a subsequent exposure to far-red rays. This is due to the fact that when exposed to far-red light, P${}_{f}r$ is converted to P${}_r$.

So, the correct answer is 'Far-red light'