The diumal changes in leaf net photosynthetíc rate (P^) in two genotypes of wheat, T. aestivum (6x) cv. Sonalika and T. monococcum (2x) cv. G 1372, were analyzed in relatíon to stomatal (4) and mesophyll (/,J limitations of P^, ribulose-1,5- bisphosphate carboxylase (RuBPC) activity and saccharides content of the leaves. Pti decreased towards the aftemoon. The /„ was mostly contributing to the diumal decline in leaf at ear emergence stage. There was a decrease in activation statě of RuBPC in the aftemoon compared to forenoon. Associated with this a marked accumulation of saccharides in wheat leaf during the day was observed. Both the genotypes showed a more or less similar pattem of diumal changes in these parameters but differed in magnitude.