Effect of water deficit stress on leaf physiological traits and drought tolerance of cotton genotypes

This study was carried out to examine the effects of drought stress on cotton leaf characteristics and its yield during 2014. The experiment was conducted in greenhouse and field conditions at Garmsar agricultural research station. The experimental design was RCBD with 3 replications arranged in split plots. Main plots and subplots designated to water stress levels and genotypes, respectively. In greenhouse, water stress decreased RWC and Excised Leaf Water Loss (ELWL). RWC of genotypes No.221, Aria, Narabri, and Sepid was higher than the others. ELWL of Aria, K8801 and K8802 was more than other genotypes whichalso their RWC was higher. ELWL of Varamin and Sahel cultivars were the lowest. At field conditions, the effects of 9, 12, 18, 24 and 30 day irrigation intervals after first flower stage, on yields of these cultivars were studied. Nine days intervals increased the yield of Varamin, Khordad and K8801 but their difference was not statistically significant. At fourth and fifth irrigation intervals,the yield of all genotypes decreased. 18 days intervals lead to yield loss too, but, because of insignificant decrease and for efficient use of water, it can be recommended that after normal irrigation from planting to first flower, to irrigate of cotton at 18 day intervals. Extension of K8801 can reduce water use and may help to permanent production.