grain physical properties of some sunflower cultivars influenced by water deficit stress

in order to investigate the water deficit impact on physical characteristics of seed in four sunflower hybrids (azargol, allstar, hysun 33 and hysun25), under three irrigation regimes (irrigation after 50, 100 and 150 mm cumulative evaporation from class a evaporation pan, respectively) and experiment was conducted. sampling was done at the end of growing period (season) when the moisture content of the seed was reached to 13%. the results showed that the maximum length, width and seed thickness were obtained from irrigation after 50 mm cumulative evaporation from pan, while irrigations after 100 and 150 mm evaporation caused to decrease the length by 15% and 24%, width by 18% and 35% and seed diameter by 17% and 30%, respectively. also, the seed width in comparison with length and seed thickness had the most susceptive to water deficit stress levels. the maximum length, width and seed thickness were seen in allstar variety. also, allstar had the highest seed weight for all levels of irrigation. there was no significant difference between allstar and hysun 25 in 50mm evaporation. therefore, the allstar hybrid had most tolerance to water deficit stress condition under all levels of irrigation in aspect of seed weight and physical properties of seed.