Comparative identification of relations among yield components under stress and normal situation can provide novel breeding strategies to plant breeders. Sesame is an oil crop with high quantity and quality of edible oil, suitable for human food. In this study, effects of limiting in avalibility of water to 15 sesame genotypes from germplasm collection of Oil Seed Crop Res. Dep on yields components was investigated. Regression analysis of seed yield on various phonologic and yield components revealed significant effects of fertile axillary branch and number of seed per capsule under normal condition and merely fertile axillary branch under water limiting situation. Comparative factor analysis between normal and water limiting conditions revealed shifting in the priority of photosynthate allocating to various organs and sinks upon water limitation. Nevertheless, axillary branches constitute the first and primary target for allocating assimilates under both normal and water limiting conditions. Under water limiting condition, plant focuses it's most strong and primary control system on number of axillary branches, followed by two successive less important and less strong control systems, which affect on seed weight, a parameter that determines plant maintenance in the nature and guarantee survival of the next generations. Focusing on the biologic behavior and relations among the behavior's components on one hand, and shifting from biometrical point of view to biometrical-physiological concepts will increase efficiency of stress breeding programs.