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

(1) Four carbon acids are the primary initial CO₂ fixation products.

(2) Effective pumping of CO₂ into bundle sheath cells.

(3) The primary fixation of CO₂ is mediated via PEP carboxylase.

(4) Rubisco in C₄ plants has higher affinity for CO₂.