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Photosynthesis and temperature notes
Last week I got into a terrible argument with a colleague about what metabolic and biochemical components of photosynthesis are sensitive to temperature. My colleague stated that if you exposed a sun-lit leaf from a plant grown at 25 °C to high leaf temperatures (say 48 °C) for a brief period of time (say 5 to 10 minutes) and then returned the leaf temperature to 25 °C that the rate of photosynthesis measured at 25 °C would decline relative to a control (a plant that had been exposed only to 25 °C). On that we both agreed. Net CO2 photosynthetic uptake decreases when leaf tissues are damaged by exposure to high temperatures.
Where we differed was on the mechanistic basis for the decline in photosynthetic rate following exposure to high temperature. He argued that the decline in photosynthesis was caused by the temperature sensitivity of photosystem I reactions. I argued that the decline in photosynthesis following leaf exposure to the high temperature was caused by the temperature sensitivity of photosystem II reactions. Then, another colleague came by and made the claim that the decline in photosynthesis following leaf exposure to high temperature was caused by the temperature sensitivity of the Hill reaction.
Now I am confused.
Last week I got into a terrible argument with a colleague about what metabolic and biochemical components of photosynthesis are sensitive to temperature. My colleague stated that if you exposed a sun-lit leaf from a plant grown at 25 °C to high leaf temperatures (say 48 °C) for a brief period of time (say 5 to 10 minutes) and then returned the leaf temperature to 25 °C that the rate of photosynthesis measured at 25 °C would decline relative to a control (a plant that had been exposed only to 25 °C). On that we both agreed. Net CO2 photosynthetic uptake decreases when leaf tissues are damaged by exposure to high temperatures.
Where we differed was on the mechanistic basis for the decline in photosynthetic rate following exposure to high temperature. He argued that the decline in photosynthesis was caused by the temperature sensitivity of photosystem I reactions. I argued that the decline in photosynthesis following leaf exposure to the high temperature was caused by the temperature sensitivity of photosystem II reactions. Then, another colleague came by and made the claim that the decline in photosynthesis following leaf exposure to high temperature was caused by the temperature sensitivity of the Hill reaction.
Now I am confused.