Redox-regulation of germination during imbibitional oxidative and chilling stress in an indica rice cultivar (Oryza sativa L., Cultivar Ratna).

Imbibitional oxidative stress of different magnitude, imposed by treatment with different titer of H2O2 (both elevated, 20 mM and low, 500 µM) to an indica rice cultivar (Oryza sativa L., Cultivar Ratna) caused formation of differential redox cues at the metabolic interface, as evident from significant alteration of ROS/antioxidant ratio, efficacy of ascorbate-glutathione cycle, radical scavenging property, modulation of total thiol content and expression of oxidative membrane protein and lipid damages as biomarkers of oxidative stress. All the redox parameters examined, substantiate the experimental outcome that treatment with elevated concentration of H2O2 caused serious loss of redox homeostasis and germination impairment, whereas low titre H2O2 treatment not only restored redox homeostasis but also improve germination and post-germinative growth. The inductive pulse of H2O2 (500 µM) exhibited significantly better performance of ascorbate-glutathione pathway, which was otherwise down-regulated significantly in 20 mM H2O2 treatment-raised seedlings. A comparison between imbibitional chilling stress-raised experimental rice seedlings with 20 mM H2O2 treated rice seedling revealed similar kind of generation of redox cues and oxidative stress response. Further, imbibitional H2O2 treatments in rice also revealed a dose-dependent regulation of expression of genes of Halliwell-Asada pathway enzymes, which is in consonance with the redox metabolic response of germinating rice seeds. In conclusion, a dose-dependent regulation of H2O2 mediated redox cues and redox regulatory properties during germination in rice are suggested, the knowledge of which may be exploited as a promising seed priming technology.