AP BIOLOGY

Detailed explanation-1: -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-2: -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.

Detailed explanation-3: -C4 plants grow better than C3 plants under hot, dry conditions when plants must close their stomata to conserve water – with stomata closed, CO2 levels in the interior of the leaf fall, and O2 levels rise.

Detailed explanation-4: -The C4 pathway initiates with a molecule called phosphoenolpyruvate (PEP) which is a 3-carbon molecule. This is the primary CO2 acceptor and the carboxylation takes place with the help of an enzyme called PEP carboxylase. They yield a 4-C molecule called oxaloacetic acid (OAA).

Detailed explanation-5: -C4 plants-including maize, sugarcane, and sorghum-avoid photorespiration by using another enzyme called PEP during the first step of carbon fixation. This step takes place in the mesophyll cells that are located close to the stomata where carbon dioxide and oxygen enter the plant.