In hot or dry conditions, plants close their stomata to conserve water. This leads to a process that competes with photosynthesis and lowers CO2 fixation. What is this process called?

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Multiple Choice

In hot or dry conditions, plants close their stomata to conserve water. This leads to a process that competes with photosynthesis and lowers CO2 fixation. What is this process called?

When leaves face hot, dry conditions, closing the stomata lowers CO2 inside the leaf while O2 from the air can accumulate. Rubisco, the enzyme that starts CO2 fixation, can also fix O2 when CO2 is scarce. This competing activity leads to the production of a metabolite that must be recycled through a complex, energy-costly pathway, releasing CO2 in the process. This sequence is photorespiration. It wastes energy and reduces net CO2 fixation, making photosynthesis less efficient under these conditions. Photolysis is the light-driven splitting of water in the light reactions, transpiration is water loss through open stomata, and the Calvin cycle is the CO2-fixing toolbar that operates when CO2 is available.

When leaves face hot, dry conditions, closing the stomata lowers CO2 inside the leaf while O2 from the air can accumulate. Rubisco, the enzyme that starts CO2 fixation, can also fix O2 when CO2 is scarce. This competing activity leads to the production of a metabolite that must be recycled through a complex, energy-costly pathway, releasing CO2 in the process. This sequence is photorespiration. It wastes energy and reduces net CO2 fixation, making photosynthesis less efficient under these conditions. Photolysis is the light-driven splitting of water in the light reactions, transpiration is water loss through open stomata, and the Calvin cycle is the CO2-fixing toolbar that operates when CO2 is available.

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