Nitric oxide donor improves adventitious rooting in mung bean hypocotyl cuttings exposed to cadmium and osmotic stresses

Abstract

Exogenous application of a nitric oxide donor, sodium nitroprusside (SNP), improved the formation and growth of adventitious roots in mung bean hypocotyl cuttings. The combined applications of SNP and CdCl2 or mannitol partially overcame the negative effects of Cd and mannitol on adventitious rooting compared with Cd or mannitol alone. SNP significantly increased the endogenous NO level and the glutathione (GSH), ascorbic acid (ASA), polyphenol, and proline (Pro) levels during the root induction and/or initiation stages. However, the malondialdehyde (MDA) levels were significantly reduced by the SNP treatment during the entire time course. To unveil the role of NO in mediating the plant response to heavy metal and osmotic stresses during adventitious rooting, SNP together with CdCl2 or mannitol was applied in the experiments. The results obtained showed that the Cd- or mannitol-induced changes in the levels of GSH, ASA, polyphenol, Pro, and MDA and the activities of ascorbate peroxidase (APX), peroxidase (POD), catalase (CAT), superoxide dismutase (SOD), and indole-3-acetic acid oxidase (IAAO) were completely or partially reversed by SNP supplementation in the SNP + Cd/mannitol treatments, suggesting that NO mediated the redox state via the regulation of antioxidative systems to prevent membrane lipid peroxidation in response to the stresses during adventitious rooting. Furthermore, the protective effects of NO on the cellular antioxidative systems under the stresses were similar to those of IBA, implying that auxin and NO shared common pathways to respond to the stresses and leading to adventitious rooting in mung bean hypocotyl cuttings under heavy metal and osmotic stresses. NO mediates the redox state and prevents membrane lipid peroxidation during adventitious rooting in plants exposed to abiotic stresses via the regulation of antioxidant levels and antioxidative enzyme activities. NO shares common signaling pathways with auxin or acts as a downstream mediator of auxin in response to abiotic stresses during adventitious rooting.