Q. Photosynthesis in $C_{4}$-plants is relatively less limited by atmospheric carbon dioxide levels because
A) Four carbon acids are the initial carbon dioxide acceptors
B) The primary fixation of carbon dioxide is mediated via PEP carboxylase
C) Effective pumping of $CO_{2}$ into bundle sheath cells
D) Rubisco in $C_{4}$- plants has higher affinity for $CO_{2}$
Explanation
The fixation of carbon dioxide in $C_{4}$-plants takes place in two places and by two different organic compounds. Phosphoenol pyruvate (PEP) is found in mesophyll cells, which primarily fixes atmospheric carbon dioxide into oxaloacetic acid (4C). RUBISCO is present in bundle sheath cells, where final fixation of carbon dioxide in hexose sugar takes place. Carbon dioxide is primarily fixed by PEP carboxylase because this enzyme has greater affinity to carbon dioxide than RUBISCO.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.