Hydrogen peroxide modulates activity and expression of antioxidant enzymes and protects photosynthetic activity from arsenic damage in rice (Oryza sativa L.)

We studied the role of H₂O₂ in the protection of photosynthesis from arsenic (As) damage in rice (Oryza sativa L.) by examining the antioxidant system, photosynthesis, and growth attributes. Among the As concentrations (0, 20, 30, 40 and 50 μM) tested, maximum oxidative stress and inhibition in photosynthesis and growth were found with 50 μM As. The application of 50 μM H₂O₂ resulted in alleviation of the adverse effects of 50 μM As on Pigment System (PS) II activity, photosynthesis, and growth. Hydrogen peroxide supplementation induced the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) and increased reduced glutathione (GSH) content and proline metabolism. The expression of SOD and APX, PSBA and PSBB was induced in the presence of H₂O₂ to alleviate the As damage to PS II and maintain photosynthetic activity. The role of H₂O₂ as a signaling molecule is shown in the protection of photosynthetic activity in rice from As toxicity through regulation on the activity and the expression of antioxidant enzymes.

Keywords: Antioxidants; Arsenic; Hydrogen peroxide; Photosynthesis; Rice.