evaluation of remobilization potential under source limited condition in iranian wheat cultivars

wheat stem reserves can be an important contributor to grain particularly under decrease in the source strength through defoliation. the aim of this research was to study ability remobilization as important contribution on yield stability under drought conditions and to investigate their intrinsic compensatory mechanism in the wheat cultivars with different degrees of resource limitations under source limited conditions. to test this hypothesis, two separate field experiments were carried out at research field of university college of agriculture and natural resources, university of tehran (located in karaj) during 2010-2011 growing seasons. first experiment was carried out in a split plot design based on rcbd that included 36 wheat cultivars and different levels of defoliation (non-defoliated control (nd), removal of all leaves (fd), removal of all leaves except the flag leaf (pd)) and the second experiment as a randomized complete block design that included 36 wheat cultivars and chlorophyll desiccation. the plants were defoliated and desiccation in 15 day after flowering growth stage. the result showed that removal of all leaves except the flag leaf (pd) and all leaves (fd) caused reduction of grain weight by 8% and 22%,  respectively. also highest grain yield were obtained of fongh cultivar in pd and fd treatment. generally cultivars with higher accumulation were less affected by defoliation treatments. wide ranges of remobilization were detected between cultivars and highest remobilization was obtained of crossed shahi cultivar. contribution of stem reserves to grain yield was by 36%.