Question

The C4 plants are photosynthetically more efficient than C3 plants because:

• A. They have more chloroplasts.
• B. The $C{O}_2$ compensation point is more.
• C. $C{O}_2$ generated during photorespiration is trapped and recycled through PEP carboxylase.
• D. The $C{O}_2$ efflux is not prevented.

Answer 1

The correct option is A They have more chloroplasts.

C4 plants are photosynthetically more efficient than C3 plants because C4 plants contain two types of chloroplast, i.e., bundle sheath chloroplast and mesophyll chloroplast. Such plants operate a dicarboxylic acid cycle in addition to the Calvin cycle. A $C{O}_2$ acceptor molecule (Phosphoenol pyruvic acid-PEP) is present in large bundle sheath cells which have higher efficiency in picking up $C{O}_2$. Thus, photosynthesis continues even at low $C{O}_2$ concentration and the rate of photorespiration is also negligible. The $C{O}_2$ compensation point is low.