Final answer:
The maximum photosynthetic rate as temperatures continue to rise is related to the temperature response of rubisco, which affects the activity of the enzyme and the rate of photosynthesis.
Step-by-step explanation:
As temperatures continue to rise, the photosynthetic rate reaches a maximum due to the temperature response of rubisco. Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is an enzyme that plays a critical role in the process of carbon fixation during photosynthesis. The activity of rubisco is highly temperature-dependent and is known to affect the rate of photosynthesis.
Because rubisco has both carboxylase and oxygenase activities, it can favor oxygenation over carboxylation at higher temperatures, leading to photorespiration, which competes with photosynthesis. This temperature response differs from the rate of plant respiration, which tends to increase more with temperature, leading to a decreased net photosynthesis at higher temperatures.
Additionally, as temperature increases, the solubility of CO₂ in water decreases, limiting the availability of this essential reactant for photosynthesis. While factors like boundary layer thickness, soil temperature, and oxygen availability can also influence photosynthesis, they play a lesser role in setting the maximum rate of photosynthesis compared to the temperature sensitivity of rubisco.