effects of source limitation and post anthesis water deficiency on grain yield and gas exchange of different barley cultivars

in this study the effects of source limitation on grain yield of twelve barley cultivars (‘aras’,‘jonub’,‘reihan’,‘zarjou’,‘sararoud’,‘sahra’,‘fajr30’,‘karoun’,‘gorgan’,‘makouei ’and ‘nosrat(’ under post anthesis water deficiency were studied. source limitation treatments were included that control, removing of awn, leaves below flag leaf, flag leaf and spike photosynthesis. all source limitation treatments significantly reduced grain yield, 1000 grain weight and number of grains per spike. in non-water stress, the highest reduction of grain yield was seen in removing of leaves below flag leaf treatment (27.6%). in water deficiency, the highest and the lowest grain yield reduction were seen in removing of spike photosynthesis (32%) and removing of awn (18.1%). flag leaf removing significantly increased photosynthesis rate in remaining leaves in non-water stress (28.8%) and water deficiency (10.8%). the evidence from this study suggests that under water deficiency after anthesis, spike photosynthesis is more important than the other current photosynthesis organs in grain yield formation in barley.