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 A Effective pumping of CO₂ in to bundle sheath cells.

The fixation of CO₂ in C₄ plants takes place in two places and by two different organic compounds. Phosphoenol pyruvate (PEP) is found in mesophyll cells which primarily fixes atmospheric CO₂ into oxaloacetic acid ( 4C).

RuBisCO is present in bundle sheath cells where fixation of CO₂ in hexose sugars takes place.CO₂ is primarily fixed by PEP carboxylase because this enzyme has greater affinity to CO₂ than RuBisCO.