To investigate the effect of exogenous application of melatonin (MT) on rice seedlings under antimony (Sb) stress, hydroponic experiments were carried out with rice seedlings (Huarun No.2). The fluorescent probe localization technology was used to locate the reactive oxygen species (ROS) in the root tips of rice seedlings, and the root viability, malondialdehyde (MDA) content, ROS (H2O2 and O2-·) content, antioxidant enzyme (SOD, POD, CAT, and APX) activities, and antioxidant (GSH, GSSG, AsA, and DHA) contents in the roots of rice seedlings were analyzed. The results showed that exogenous addition of MT could alleviate the adverse effects of Sb stress on the growth and increase the biomass of rice seedlings. Compared with the Sb treatment, the application of 100 μmol·L-1 MT increased rice root viability and total root length by 44.1% and 34.7% and reduced the content of MDA, H2O2, and O2-· by 30.0%, 32.7%, and 40.5%, respectively. Further, the MT treatment increased the activities of POD and CAT by 54.1% and 21.8%, respectively, and also regulated the AsA-GSH cycle. This research indicated that exogenous application of 100 μmol·L-1MT can promote the growth and antioxidant ability of rice seedlings and alleviate the damage of lipid peroxidation by Sb stress, thus improving the resistance of rice seedlings under Sb stress.
Keywords: AsA-GSH cycle; antimony stress; antioxidant system; melatonin(MT); rice.