PHOTOSYNTHESIS
PHOTORESPIRATION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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It is hot and dry outside.
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It is cool and damp outside.
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It is hot and damp outside.
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It is cool and dry outside.
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Detailed explanation-1: -C3 plants have the disadvantage that in hot dry conditions their photosynthetic efficiency suffers because of a process called photorespiration. When the CO2 concentration in the chloroplasts drops below about 50 ppm, the catalyst rubisco that helps to fix carbon begins to fix oxygen instead.
Detailed explanation-2: -As a plant’s environment becomes hot, dry, and bright, its stomata, where carbon dioxide enters the leaf, tend to close. This lowers the concentration of carbon dioxide into the Calvin cycle, causing the cycle to accept oxygen in place of the carbon dioxide and makes a new product.
Detailed explanation-3: -Why does photorespiration happen? If it is too hot or dry, plants often close their stomata to prevent water loss. This prevents CO2 from entering the leaf, as well as prevents O2 from exiting. Oxygen builds up inside the leaf and photorespiration happens instead of the Calvin cycle.
Detailed explanation-4: -C3 plants do not have the anatomic structure (no bundle sheath cells) nor the abundance of PEP carboxylase to avoid photorespiration like C4 plants.
Detailed explanation-5: -The high temperature will make the plant close its stomata to reduce water loss by evaporation. If the stomata is closed, the oxygen from photosynthesis will build up inside the leaf while the carbon dioxide will not get into the leaf.