[Responses of root physiological characteristics of different drought-tolerant cotton varieties to drought].

In order to explore the physiological responses of root system of different drought-resistant cotton varieties to drought and their relationships with biomass, we examined the effects of drought stress on root vigor, antioxidant enzyme activities and anatomic structure (duct diameter, number) and biomass of different drought-tolerant varieties, including the drought-inolerant variety 'Xinluzao 17' (L17) and the drought-tolerant variety 'Xinluzao 22' (L22). Both varieties were grown under soil column cultivation conditions, with conventional irrigation (CK), mild drought (W1) and moderate drought (W2) treatments. The results showed that drought stress caused significant reductions in soluble protein (SP) content, root vigor (RV), the number of cork layers, the number of rhizome ducts, the diameter of the ducts in both varieties. The higher root MDA content, CAT, POD and SOD activities in response to drought led to reduction of aboveground dry mass. Compared with that of L17, SP content, 0-40 cm and 80-120 cm soil layer RV, the number of cork layers, the number of rhizome ducts, the diameter of ducts, and the aboveground dry mass of L22 all signi-ficantly increased. Under the W2 treatment, the RV decrease of L22 was 26.2% lower than that of L17, and CAT, POD, SOD activities and the thickness of cortex were 43.6%, 6.9%, 25.4%, 19.9% higher than that of L17. There were positive correlations between dry mass and RV, SOD, POD, the number of cork layers, the diameter and number of rhizome ducts. Therefore, cotton variety with strong drought tolerance could maintain higher root activity, cork layer number, the diameter of rhizome ducts, and number under drought conditions, and thus promote the accumulation of aboveground biomass, which was the physiological mechanism for their stronger drought tolerance.