NEET2005BotanyPhotosynthesis in Higher PlantsActual
Photosynthesis in C ₄ plants is relatively less limited by atmospheric CO ₂ levels because:
Options
- Aeffective pumping of CO ₂ into bundle sheath cells
- Brubisco in C ₄ plants has higher affinity, for CO ₂
- Cfour carbon acids has the primary initial CO ₂ fixation products
- Dthe primary fixation of CO ₂ is mediated via PEP carboxylase.
Correct answer
A. effective pumping of CO ₂ into bundle sheath cells
Step-by-step solution
In C ₄ plants, initial fixation of carbon dioxide occurs in mesophyll cells. The primary acceptor of CO ₂ is phosphoenol pyruvate or PEP. It combines with carbon dioxide in the presence of PEP carboxylase or PEPcase to form oxaloacetate. C ₄ plants are more efficient in picking up CO ₂ even when it is found in low concentration because of the high affinity of PEPcase. Related Theory The two key restrictions slow down photosynthesis in C₃ cycle: (i) Rubisco aims to fix carbon dioxide, but can also fix oxygen molecul