a study about some physiological indices of sunflower growth under drought stress

in order  to study the effect of drought stress on some growth indices of oil sunflower cultivars, a study was conducted in isfahan. the experiment was conducted as split plots in a randomized complete blocks design with three replications in isfahan (51° 48' e, 32° 40' n).main plots were drought stress in four levels (80, 100, 120, and 140 mm evaporation from evaporation pan class a and cultivars were sub plots (sirena, record, euroflore). total dry weight, leaf area index, net assimilation rate and crop growth rate were measured. results showed that total dry matter, leaf area index, net assimilation rate and crop growth rate were decreased by drought increasing from 80 to 140mm.  the least evaporation (80mm) had the highest amount of mentioned traits. among cultivars, record had higher total dry weight because of having growth period and then higher lai, stem dry weight, leaf dry weight and capitulum dry weight but it had lower nar and cgr because of higher lai and shading of upper leaves, then it is recommended to use record cultivar.