If the bath was set to 80 â°c, what do you think would happen to the rate of photosynthesis?

The right answer is D, the plant cannot perform photosynthesis at 80°C, neither respiration or any metabolism and the plant would die.

Temperature affects first micromolecules by increasing their molecular thermic agitation and affect also macromolecules like DNA, protein and especially enzymes, by changing their conformation and denaturating them.