Why is temperature important for photosynthesis, and what happens at high temperature?

Why is temperature important for photosynthesis, and what happens at high temperature?

• A. Temperature has no effect on photosynthesis.
• B. Higher temperatures always increase the rate of photosynthesis.
• C. Temperature only affects stomatal movement.
• D. Enzyme activity depends on temperature; high temps reduce enzyme efficiency, increase photorespiration, and can denature enzymes.

Answer: (D)

Temperature affects photosynthesis because the process relies on enzymes to drive the chemical steps. Each enzyme has an optimal temperature, and within that range the reactions run smoothly, so the rate can rise as temperature increases. But when temperatures get too high, enzymes can lose their shape and function (denature), so the rate drops. At high temperatures, several problems stack up. The efficiency of the key enzyme involved in carbon fixation decreases, and the balance between carbon dioxide and oxygen processing by RuBisCO shifts toward oxygenation, increasing photorespiration and wasting energy. Heat can also disrupt chloroplast membranes and pigments, further lowering the plant’s ability to capture light energy. So, rather than always speeding things up, high temperature often reduces photosynthesis due to enzyme instability, more photorespiration, and damage to the photosynthetic machinery.

Temperature affects photosynthesis because the process relies on enzymes to drive the chemical steps. Each enzyme has an optimal temperature, and within that range the reactions run smoothly, so the rate can rise as temperature increases. But when temperatures get too high, enzymes can lose their shape and function (denature), so the rate drops.

At high temperatures, several problems stack up. The efficiency of the key enzyme involved in carbon fixation decreases, and the balance between carbon dioxide and oxygen processing by RuBisCO shifts toward oxygenation, increasing photorespiration and wasting energy. Heat can also disrupt chloroplast membranes and pigments, further lowering the plant’s ability to capture light energy. So, rather than always speeding things up, high temperature often reduces photosynthesis due to enzyme instability, more photorespiration, and damage to the photosynthetic machinery.