As temperature rises, how does photosynthesis in turfgrass typically change?

• A. Food production decreases but the amount of oxygen increases as temperatures rise.
• B. Food production increases and oxygen increases.
• C. Both decrease.
• D. Both increase equally.

Answer: (A)

Photosynthesis in turfgrass responds to temperature by speeding up as temps rise toward the plant’s optimum, then slowing down when heat stress becomes limiting. Enzymes that drive carbon fixation work more efficiently at moderate warmth, so more carbohydrates are produced at first. If temperatures climb past the optimum, those enzymes can be damaged or inhibited, and stomata may close to reduce water loss, which limits CO2 uptake and lowers carbohydrate production. The oxygen released by the leaf comes from the light reactions of photosynthesis, so its production generally follows the same pattern as photosynthesis: it increases as photosynthesis increases with temperature toward the optimum, and decreases when photosynthesis declines under heat stress. In typical turfgrass responses, you wouldn’t expect food production to go down while oxygen production goes up with rising temperature; both usually rise together up to the optimum and fall together under heat stress.