Question

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

• A. there is effective pumping of CO₂ into bundle sheath cells
• B. RuBisCO in C₄ plants has higher affinity for CO₂
• C. six carbon acids are the primary initial CO₂ fixation products
• D. the primary fixation of CO₂ is mediated via PEP carboxylase

Answer 1

Answer: (D)

CO₂ acceptor molecule in C₄ plants is phosphoenol pyruvate (PEP). C₄ plants are more efficient in picking up CO₂ even when it is found in low concentration because of high affinity of PEP. PEP carboxylase (PEPcase) is the key enzyme which catalyses the primary fixation of CO₂.