Relations Between Barley Root Traits and Osmotic Adjustment Under Terminal Drought Stress

The root responses to water deficit and osmotic adjustment are two main mechanisms that plants use to cope with drought stress. In order to evaluate relations between these mechanisms a greenhouse study was carried out in factorial based on CRD with three replications. In present work, three barley cultivars with different levels of drought tolerance have been subjected to terminal drought stress. Water stress was imposed by withholding water at the anthesis stage. The samplings were done when the available water content (AWC) in soil reached to 30% AWC (moderate stress) and 10% AWC (severe stress). Biological yield (BY) and grain yield (GY) were calculated at the end of the growth period. The results indicated that by increasing water stress severity, water potential (WP), osmotic potential (OP) and root volume (RV) decreased. In contrast, osmotic adjustment (OA) was higher in drought tolerant cultivar, Yousof, in severe drought stress condition (10% AWC). It seems that osmotic adjustment significantly caused to increase root to shoot ratio in this cultivar. Finally, the lowest grain yield reduction obtained from Yousof. The significant correlations were obtained between OA and root traits (p<0.05) in 10% AWC condition. The highest significant correlations were observed between OA and RWC (r=+0.92), BY (r=+0.83), GY (r=+0.96) in 10% AWC condition (p<0.01). The results underline the efficient relations between different drought resistance mechanisms especially in drought tolerant cultivar.