With regard to photosynthesis, photorespiration ____.
A) is more efficient in producing carbohydrates
B) predominates in C₃ plants in cool weather when water is plentiful
C) predominates in C₄ plants on hot days
D) produces the same amount of PGA
E) is less efficient in producing carbohydrates

Question

With regard to photosynthesis, photorespiration ____.
A) ​is more efficient in producing carbohydrates
B) ​predominates in C₃ plants in cool weather when water is plentiful
C) ​predominates in C₄ plants on hot days
D) ​produces the same amount of PGA
E) is less efficient in producing carbohydrates​

Quizplus · Accepted Answer

Photorespiration is a wasteful process that occurs when the stomata are closed, and carbon dioxide cannot get into the plant. Instead, oxygen binds to the active site of rubisco, leading to the production of toxic metabolites and the breakdown of carbohydrates. Compared to the normal photosynthetic pathway, photorespiration is less efficient in producing carbohydrates because it consumes ATP and reduces the amount of carbon available for the Calvin cycle. Thus, photorespiration is a negative side effect of the evolution of C3 plants, which prioritize water conservation over carbon fixation. C4 plants and CAM plants have evolved alternative mechanisms to minimize photorespiration and increase photosynthetic efficiency in hot and arid environments.

With Regard to Photosynthesis, Photorespiration ____