• # question_answer Photosynthesis in ${{\text{C}}_{\text{4}}}$ plants is relatively less and limited by atmospheric $\text{C}{{\text{O}}_{\text{2}}}$levels because of A)  Effective pumping of $\text{C}{{\text{O}}_{\text{2}}}$into bundle sheath cells.B)  Rubis CO in ${{\text{C}}_{\text{4}}}$ plants has higher affinity for$C{{O}_{2}}.$C)  Four carbon acids are the primary initial $C{{O}_{2}}.$fixation products.D)  The primary fixation of $C{{O}_{2}}$ is mediated through PEP carboxylase.

In${{C}_{4}}$plants, the initial fixation of carbon dioxide occurs in mesophyll cells. The primary acceptor of$C{{O}_{2}}$is phosphoenolpyruvate or PEP. It combines with carbon dioxide in the presence of PEP carboxylase or PEP Case to form oxaloacetate. ${{C}_{4}}$plants are more efficient in picking up $C{{O}_{2}}$even when it is found in low concentration because of the high affinity of PEP Case.