effect of water deficit stress on agronomic characteristics of sunflower hybrids

in order to study the effect of water deficit effects on agronomic characteristics of sunflower ‎hybrids, three separate experiments were conducted as‏ ‏randomized complete block design with ‎three replications at the research field of seed and plant improvement institute - karaj. the first ‎experiment conducted at optimum conditions and plants were irrigated after 60 mm evaporation ‎from evaporation pan at germination stage till end of growing period, whereas the second and third ‎experiments were irrigated after 120, 180 mm evaporation from evaporation pan, class a, ‎respectively, and were considered as water deficit conditions. the results showed significant effects ‎of water deficit on 75 percent flowering stage, 1000 seed weight, seed number per plant, seed yield, ‎productivity effort, harvest index and seed oil content. sever water deficit caused the decrease of ‎seed yield to 500 kg ha-1 (83 percent reduction) which was due to decrease of 1000 seed weight (50 ‎percent) and seed number per plant (54 percent). also, allstar produced the highest yield in ‎medium and severe water deficit and the mehr was superior to other hybrids in normal condition.‎