Effect of Ascorbate-Glutathione (AsA-GSH) Cycle on Hg2+-Tolerance in Rice Mutant

The rice (Oryza sativa L.) cultivar Zhonghua 11 and an Hg2+-tolerant rice mutant were cultured in solution for investigating the reactive oxygen species (ROS) metabolism and the dynamic change of ascorbate-glutathione (AsA-GSH) cycle in response to 0.4 mmol L−1 Hg2+ treatment. The evolution rate of superoxide radical (O2) and the contents of H2O2, malondialdehyde (MDA), oxidized glutathione (GSSG), and docosahexaenoic acid (DHA) of the leaves were higher in the wild type than in the mutant. The ratio of GSH to GSSG and the ratio of AsA to DHA were higher in the mutant than in the wild type, while the accumulation of Hg2+ in roots and stems of the mutant was more than that in the wild type. These results indicated that the AsA-GSH cycle was less inhibited in the mutant than in the wild type, and the mutant was thus able to scavenge ROS more. An effective AsA-GSH cycle is important for the mercury resistance of mutant.