effect of post-anthesis drought stress on contribution of stem reserves in grain yield of different wheat cultivars

concinciding of wheat growth in post-anthesis period by water deficiency can result in reduction of current photosynthesis. in this circumstance stem-stored carbohydrate from pre-anthesis period had an important role in supporting assimilates for growing grain. an experiment was conducted in 2007-8 in experimental farm of arsanjan islamic azad university, in order to investigation the quantity of stem reserves in different wheat cultivars of different height. the randomized block, split-plot design was used in the experiment. main plots consisted of three irrigation regimes (full irrigation, only one irrigation in post-anthesis and without irrigation during post-anthesis period) and subplot consisted of six wheat cultivars (marvdasht, falat, ghods, karaj3, adl and kaveh). the results showed that water holding in post-anthesis period significantly reduced grain yield, biological yield, grain weight and stem weight. grain yield, biological yield, harvest index, number of ear m-2, number of seed ear-1 and plant height significantly differed between cultivars. the interaction effects of cultivars and irrigation indicated that different cultivars respond differently to reduction of irrigation. by withholding post-anthesis irrigation the adverse effects of drought on grain weight and grain yield in tall cultivars was lower in comparison with dwarf cultivars. losses of stem weight with irrigation withholding were higher in tall cultivars. these results indicated that tall cultivars have more stored reserves in stem, which can be used in unfavourable condition for grain filling. by the other word remobilization is higher in tall cultivars and this trait can be used for developing drought tolerance in breeding programs.