Which adaptations reduce photorespiration and water loss?

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Multiple Choice

Which adaptations reduce photorespiration and water loss?

Plants have different strategies to keep photosynthesis efficient in hot, dry conditions. The main idea is to reduce photorespiration, which happens when the enzyme Rubisco fixes oxygen instead of carbon dioxide, especially when CO2 inside the leaf is low due to closed stomata in heat. Both CAM and C4 pathways are adaptations that increase carbon fixation efficiency and lower water loss. CAM plants open their stomata at night to take in CO2 and store it as malic acid. During the day, they close their stomata and release the CO2 from the stored acids for the Calvin cycle, keeping water loss very low while still supplying CO2 for photosynthesis. C4 plants initially fix CO2 with a different enzyme in mesophyll cells into a four-carbon compound, which is then shuttled to bundle-sheath cells where CO2 is released for the Calvin cycle. This CO2 concentration around Rubisco greatly reduces photorespiration and allows the stomata to stay partly closed, conserving water. Because both strategies reduce photorespiration and enhance water-use efficiency, they outperform C3 plants in hot, dry environments.

Plants have different strategies to keep photosynthesis efficient in hot, dry conditions. The main idea is to reduce photorespiration, which happens when the enzyme Rubisco fixes oxygen instead of carbon dioxide, especially when CO2 inside the leaf is low due to closed stomata in heat. Both CAM and C4 pathways are adaptations that increase carbon fixation efficiency and lower water loss.

CAM plants open their stomata at night to take in CO2 and store it as malic acid. During the day, they close their stomata and release the CO2 from the stored acids for the Calvin cycle, keeping water loss very low while still supplying CO2 for photosynthesis. C4 plants initially fix CO2 with a different enzyme in mesophyll cells into a four-carbon compound, which is then shuttled to bundle-sheath cells where CO2 is released for the Calvin cycle. This CO2 concentration around Rubisco greatly reduces photorespiration and allows the stomata to stay partly closed, conserving water.

Because both strategies reduce photorespiration and enhance water-use efficiency, they outperform C3 plants in hot, dry environments.

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