Question

With reference to factors affecting the rate of photosynthesis which of the following statements is not correct?

• A. Light saturation for CO2 fixation occurs at 10% of full sunlight?
• B. Increasing atmospheric CO2 concentration up to 0.05% can enhance CO2 fixation rate?
• C. C3 plants respond to higher temperatures with enhanced photosynthesis while C4 plants have much lower temperature optimum?
• D. Tomato is a greenhouse crop that can be grown in CO₂ – enriched atmosphere for a higher yield?

Answer 1

The correct option is C

C3 plants respond to higher temperatures with enhanced photosynthesis while C4 plants have much lower temperature optimum?

The correct option is C.

Explanation of the correct option:

1. C3 plants have the RuBisCo enzyme which gets activated at higher carbon dioxide concentration.
2. C4 plants have PEP as a major CO₂ acceptor.
3. Photosynthetic activity is mostly affected by enzymes rather than temperatures.
4. High temperature leads to the destruction of photosynthetic pigments.
5. So, C3 plants will not respond to higher temperatures with enhanced photosynthesis.

Explanation of the incorrect options:

Option A:

1. Light saturation may occur at 50% of full sunlight.
2. So, light saturation for Carbon dioxide fixation occurs at 10% of full sunlight.

Option B:

An increase in CO2 concentration increases the rate at which carbon is incorporated to form carbohydrates in the light-independent reaction.

Option D:

Crops such as tomatoes allowed to grow in a carbon dioxide-rich environment show higher yields.

Final answer: C3 plants respond to higher temperatures with enhanced photosynthesis while C4 plants have much lower temperature optimum, is the wrong statement concerning factors affecting the rate of photosynthesis.