Question
.Why would it be hard to find the ideal light intensity if the temperature were very hot or cold?
Answers
Answered by
GPT-5 mini
Because temperature strongly affects the biochemical and physiological processes that control photosynthesis, extreme hot or cold conditions stop light from being the main limiting factor. Concretely:
- Photosynthetic enzymes (e.g., Rubisco) have an optimal temperature range. When it’s too cold they work very slowly; when it’s too hot they denature or lose efficiency. In either case increasing light won’t raise the photosynthetic rate much, so you can’t find a meaningful “ideal” light level.
- At high temperatures stomata often close to conserve water, reducing CO2 entry. Without CO2, extra light can’t be used for carbon fixation and may instead cause photodamage.
- Very high light together with heat can cause photoinhibition and damage the photosynthetic apparatus, so the plant’s response to light becomes non‑linear and unstable.
- Respiration increases with temperature, so net photosynthesis may drop even if gross photosynthesis rises; that confounds finding an optimal light intensity.
- Extreme temperatures also stress the plant, increasing variability and making measurements noisy and unreliable.
In short, when temperature is far from optimal it becomes the limiting or damaging factor, so light intensity no longer shows a clear “ideal” effect.
- Photosynthetic enzymes (e.g., Rubisco) have an optimal temperature range. When it’s too cold they work very slowly; when it’s too hot they denature or lose efficiency. In either case increasing light won’t raise the photosynthetic rate much, so you can’t find a meaningful “ideal” light level.
- At high temperatures stomata often close to conserve water, reducing CO2 entry. Without CO2, extra light can’t be used for carbon fixation and may instead cause photodamage.
- Very high light together with heat can cause photoinhibition and damage the photosynthetic apparatus, so the plant’s response to light becomes non‑linear and unstable.
- Respiration increases with temperature, so net photosynthesis may drop even if gross photosynthesis rises; that confounds finding an optimal light intensity.
- Extreme temperatures also stress the plant, increasing variability and making measurements noisy and unreliable.
In short, when temperature is far from optimal it becomes the limiting or damaging factor, so light intensity no longer shows a clear “ideal” effect.
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