Temperature limits photosynthesis when it is:
Athe same as the surrounding air temperature
Bthe only factor present in the leaf
Chigh enough to denature the enzymes involved
Dabove the carbon dioxide concentration
Answer & Solution
Correct answer: C. high enough to denature the enzymes involved
1. A factor limits photosynthesis when it is the one holding the rate down.
2. Photosynthesis is enzyme-controlled, and enzymes are proteins.
3. At high temperatures those enzymes denature, so the rate falls even when light and carbon dioxide are plentiful.
4. At low temperatures the enzymes work slowly, which also limits the rate.
5. Comparing temperature with carbon dioxide concentration is meaningless, since the two are measured in different units.
_Source: NECTA ACSEE 2023 Biology 133/1, Question 6: Nutrition_