Question

Photosynthesis in C4-plants is relatively less limited by atmospheric CO₂ levels because

• A. Effective pumping of CO₂ in to bundle sheath cells.
• B. RuBisCO in C4 -plants has higher affinity for CO₂.
• C. Four carbon acids are the primary initial CO₂ fixation products.
• D. The primary fixation of CO₂ is mediated via PEP carboxylase.

Answer 1

The correct option is D)

Plants such as sugarcane and sorghum fix atmospheric carbon dioxide into phosphoenol pyruvic acid to produce oxaloacetic acid (a four-carbon acid) in the presence of phosphoenolpyruvate carboxylase (PEP carboxylase). Such plants are called $C_4$ plants. In $C_4$ plants, the primary product of OAA is mediated by PEP carboxylase, so it is relatively less limited by atmospheric ${CO}_2$ levels.

So, the correct answer is 'The primary fixation of ${CO}_2$ is mediated via PEP carboxylase'.