The activities of key C4 photosynthetic enzymes including phosphoenolpyruvate carboxylase (PEPcase), NADP-malic
enzyme (NADP-ME), malate dehydrogenase (MDH) and pyruvate phosphate dikinase (PPDK) were assayed in flag leaves
at three major growth stages (heading, anthesis and grain filling) among 59 winter wheat genotypes grown in field
conditions. All C4 enzymes expressed in the flag leaves and their activation showed a wide range of variation in relation
to different growth stages in all the genotypes. PEPcase, NADP-ME and MDH displayed the highest mean activities of
1.018, 0.758 and 0.731 µmol. min–1.mg–1 protein at heading stage, respectively; while PPDK showed the highest mean
activity (0.888 µmol. min–1.mg–1 protein) at grain filling stage. The activities of PEPcase and PPDK were higher at
heading stage, decreased at anthesis and again increased at grain filling stage, while NADP-ME and MDH exhibited a
decreasing trend at the three stages. The results of the current study could be valuable and useful for wheat researchers
in improving photosynthetic capacity of wheat.