Which limitation affects C4 photosynthesis pathways’ efficiency in cold environments approaching freezing?

💡 Explanation

When temperatures nearing freezing decrease the kinetic energy of molecules, the PEP carboxylase enzymatic activity slows significantly because enzyme catalysis rates diminish dramatically, hindering efficient initial carbon fixation. Therefore reduced PEP carboxylase activity limits overall process efficiency, rather than limitations related to pigment absorption, substrate availability, or stomata closure, which are independently affected.

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