Nitric Oxide Alleviates Iron Toxicity by Reducing Oxidative Damage and Growth Inhibition in Wheat (Triticum aestivum L.) Seedlings

Abstract

Nitric oxide (NO) is an important bioactive signaling molecule in plants which modulates a variety of physiological processes and responses to abiotic and biotic stresses. In this study, the effects of exogenous NO supplied as sodium nitroprusside (SNP) in wheat seedlings under ironinduced oxidative damage was investigated. An appropriate concentration of NO was determined by conducting a preliminary experiment. In solution culture, wheat seeds were grown in the control (100 μM Fe), and toxic Fe (400 μM Fe) levels and the toxic Fe supply was treated with various levels of (50, 100, 200 and 500 μM) sodium nitroprusside (SNP). The results indicated that 400 μM Fe significantly decreased percentage germination, tolerance index, root lengths as well as fresh and dry weight compared to control. Exogenous SNP attenuated the inhibition of wheat seed germination. The promoting effect was most pronounced at 100 μM SNP. The accumulated concentration of iron and active Fe was significantly decreased by SNP treated Fe toxic seedlings. Toxicity of Fe caused oxidative stress by elevating hydrogen peroxide (H2O2), malondialdehyde (MDA) and proline contents in roots of wheat seedlings. One hundred μM SNP counteracted Fe toxicity by reducing the H2O2, MDA and proline contents of toxic Fe exposed seedlings. Meanwhile, application of SNP markedly reduced the activities of superoxide dismutases (SOD), catalases (CAT), peroxidase (POD), ascorbate peroxidases (APX), non protein thiols (NPT) and of glutathione reductase (GR) and increased ascorbate (ASc) compared with Fe toxic treatment alone, thereby indicating the modulation of the antioxidative capacity in the root under Fe stress by NO. The results indicated that the exogenous application of SNP, improved the antioxidant enzymes activity of wheat seedlings against Fe induced oxidative stress.