Response of wheat cultivars to source size reduction at flowering stage: grain number and weigh, Chlorophyll stability and stem reserves

Studies manipulating the source-sink relationships during post anthesis in wheat have shown inconsistent results، concluding that wheat yield could be either sinkor source-limited. The aim of this study was to determine source limitation degree of 36 Iranian wheat cultivars andto investigate their intrinsic compensatory mechanism in response to source size reduction. A split plot design based onrandomized complete block designwas carried out with 3 replications. Treatment 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)). Defoliation was carried out at flowering stage. A wide range of responses to defoliation treatments observed among the cultivars، suggesting a high variation in sink or source limitation among the cultivar while them were cultivars with no response sever leaf defoliation (FD) same cultivars different even by mild leaf defoliation (PD)، thatimplying to possible various compensatory mechanism in cultivars.