Abscisic acid improves drought tolerance of triploid bermudagrass and involves H2O2- and NO-induced antioxidant enzyme activities

Drought is a major limiting factor for turfgrass growth. Protection of triploid bermudagrass against drought stress by abscisic acid (ABA) and its association with hydrogen peroxide (H2O2) and nitric oxide (NO) were investigated. ABA treatment increased relative water content, decreased ion leakage and the percentage of dead plants significantly under drought stress. Superoxide dismutase (SOD) and catalase (CAT) activities increased in both ABA-treated and control plants, but more in ABA-treated plants, under drought stress. Malondialdehyde, an indicator of plant lipid peroxidation, was lower in ABA-treated plants than in control plants, indicating that ABA alleviated drought-induced oxidative injury. ABA treatment increased H2O2 and NO contents. ABA-induced SOD and CAT activities could be blocked by scavengers of H2O2 and NO, and inhibitors of H2O2 and NO generation. The results indicated that H2O2 and NO were essential for ABA-induced SOD and CAT activities. Both H2O2 and NO could induce SOD and CAT activities individually. SOD and CAT induced by H2O2 could be blocked by scavenger of NO and inhibitors of NO generation, while SOD and CAT induced by NO could not be blocked by scavenger of H2O2 and inhibitor of H2O2. The results revealed that ABA-induced SOD and CAT activities were mediated sequentially by H2O2 and NO, and NO acted downstream of H2O2.