CBSE Class 10 Answered

The dark reactions of photosynthesis being enzymatic are temperature controlled. At higher temperatures, the rate of photosynthesis decreases largely as a result of enzyme denaturation.

Also when the temperature is very high, the guard cells (stomata) close. When the stomata close, gaseous exchange will no longer be occurring so therefore CO2 levels drop rapidly within the leaf, inhibiting the light-independent reactions. This then causes photosynthesis to reduce or stop.

Enzymes are the catalyst used for the photosynthesis reaction. Enzymes work by colliding with the hydrogen and carbon dioxide. It is shaped to only accept hydrogen and carbon dioxide molecules. A rise in temperature provides more heat energy, which the enzymes absorb to work faster. They work faster by colliding more frequently. Because of that, it produces more glucose quickly. A lower temperature therefore will mean lowered rate of photosynthesis, due to less heat energy.