Question:

Which of the following statements is correct?

Photorespiration is useful process.

C3 plants are more efficient than C4 plants.

Photorespiration is absent in C3 plants but present in C4 plants.

C4 plants are more efficient than C3 plants.

Solution:

C4 plants are more efficient than C3 plants because they have little photorespiration while in C3 plants more than half of photosynthetic carbon is lost in photorespiration. C4 plants are more efficient in picking up CO2, even in low CO2 concentration because of the high affinity of CO2 with PEP (phosphoenol pyruvic acid).