a study of some physiological aspects of yield in drought tolerant vs susceptible wheat (triticum aestivum l.) cultivars under post anthesis drought stress conditions

drought stress is a major factor limiting crop production. investigation of physiological characteristics related to drought tolerance and crop production may be useful in selecting drought tolerant cultivars as well as in improving crop yield. two drought tolerant (azar2 & back cross roshan) and two drought susceptible (marvdast & shiraz) cultivars were investigated in both greenhouse and field experiments. post-anthesis drought stress caused decrease in relative water content (rwc), photosynthetic rate, leaf area durability duration, chlorophyll content, biomass production, harvest index as well as grain yield. drought tolerant cultivars exhibited higher rwc, stem reserve remobilization and lower yield losses compared to susceptible cultivars. high stem reserve remobilization resulted in grain yield stability under drought stress conditions. among the yield components only thousand seed weight was reduced by post-anthesis drought stress. both source and sink limitation appeared to be responsible for reduction of thousand seed weight under drought stress conditions. rwc was significant and positively correlated with photosynthetic rate and with grain yield. rwc was higher in tolerant cultivars than in susceptible ones. thus rwc could be used as a useful marker for selecting drought tolerant cultivars. high stem reserve remobilization may result in yield stability and lower reduction of yield under post-anthesis drought stress conditions