Paeonol (Extracted from Paeonia suffruticosa Root) Pretreatment Lends Antioxidant Protection against Arsenite Stress in Rice (Oryza sativa L.) Seedlings

Background: Arsenic toxicity has become a growing concern for rice growers in South East Asian countries due to the extensive use of arsenite-contaminated groundwater in rice paddies. The presence of arsenic in soil and water from irrigation results in impaired crop growth and development. The effect of exogenous pretreatment of paeonol on hydroponically grown rice seedlings was examined by investigating the antioxidant systems under arsenic stress.
Methods: In the experiment, 7-day old rice seedlings (IR-64) were exposed to 10, 50, 100 µM of arsenite separately and co-treatment with 10, 50, 100 µM paeonol (extracted from Paeonia suffruticosa root) in a hydroponic medium for 7 days. The activity of lipid peroxidation [malondialdehyde] antioxidants [APX, CAT, SOD, GPX] in root and shoot tissue were determined by standard protcol.
Result: Arsenite treatments inhibited growth correlating with increased arsenic accumulation in rice seedlings. Oxidative stress was induced by overproduction of reactive oxygen species (ROS) and disruption of antioxidant defense systems measured in terms of increased activity of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, glutathione peroxidase, catalase  and lipid peroxidation (malondialdehyde) in root and shoot tissues separately. Paeonol pretreated seedlings along with arsenic exposure substantially decreased the level of arsenic uptake in plants resulting in comparatively higher plant growth as well as biomass substantial reduction in ROS overproduction and MDA content was observed in paeonol pretreatment as compared to arsenic-exposed seedlings alone. These findings indicate that paeonol has an ameliorating effect on arsenite-induced oxidative stress, suggesting that paeonol enhances the activity of antioxidants and prevents oxidative stress damage by transforming ROS to a neutral and non-toxic end product. Such natural ameliorative methodology will enhance agricultural production in arsenic stressed paddy field environments.