What is one potential reason for why a plant may experience diminished photosynthetic rates?
One of the most common reasons is occurrence of photorespiration process. When the temperature of the environment increases, stomata close and thus, carbon dioxide is not delivered to mesophyll cells. At the same time, light-dependent reactions of photosynthesis proceed and oxygen is produced. Thus, the ratio between oxygen and carbon dioxide increases. It causes inclusion of oxygen instead of carbon dioxide into the first reaction of Calvin cycle catalyzed by RuBisCO. As a result, glucose production does not take place and the rate of photosynthesis decreases.