Question

The rate of photosynthesis does not depends upon

• A. Light duration
• B. Light intensity
• C. Light quality (colour)
• D. Temperature

Answer 1

The correct option is A Light duration

In presence of all favourable environmental conditions, a 10-degree increase in temperature doubles the rate of photosynthesis up to the optimum temperature 25 degrees. Beyond the optimum temperature, rise in temperature causes denaturation of enzymes and thereby declines the rate of photosynthesis.

The rate of photosynthesis is maximum in blue (420-480 nm) and red (640-670 nm) region of light which are absorbed by chlorophyll. There is minimum/no photosynthesis in green and other parts of light which are not absorbed by photosynthetic pigments.

The increase in the light intensity increases the photosynthetic absorption of $C{O}_2$ and release of oxygen gas which in turn balances the gaseous exchange through cellular respiration and thereby bringing the plant to the light compensation point. Beyond this point increases in light intensity increases the photosynthetic release of oxygen.

The duration of light does not affect the rate of photosynthesis as it does not affect the absorption of light by chlorophyll.

So, the correct answer is option A.