Question

A plant is exposed to an optimum amount of light intensity, with a limited supply of CO${}_2$. As the carbon dioxide concentration increases

• A. The rate of photosynthesis increases
• B. The rate of photosynthesis decreases
• C. The rate of photosynthesis remains constant
• D. None of the above

Answer 1

The correct option is A The rate of photosynthesis increases

Blackman's law of limiting factors are the various factors which affect the rate of photosynthesis. It is considered that when the other factors are constant, the factor which is least or minimum has the direct effect on the rate of photosynthesis. When the light intensity is maintained at the optimum level, the other factor which is CO${}_2$ supply is reduced. This causes the rate of reaction to completely depend on CO${}_2$. When the carbon dioxide concentration increases, the rate of reaction increases.

Thus, the correct answer is option A.