In order to study the effcts of multi-wall carbon nanotubes and sodium nitroprusside (SNP) on seedling growth, and physiological indices of barley under salinity stress an experiments was carried out in a factorial arrangement based on a completely randomized design with three replications. Multi-walled carbon nanotubes at concentrations of 500, 1000 and 2000 mg kg-1 in soil and foliar application of sodium nitroprusside at 100 μm under salinity stress (0, 50 and 100 mM sodium chloride) were used. Based on the results, the presence of multi-wall carbon nanotubes in soil with foliar application of SNP improve the growth and physiological parameters of barley under salinity stress. By employing nanomaterials and SNP, the relative water content, proline, as well as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities increased. Using 100 μm SNP with multi-walled carbon nanotubes (500 mg kg-1) increased SOD activity by 27.4 and 29% under 200 mM salinity stress. In the current experiment, improving the antioxidant system of barley was associated with a reduction in malondialdehyde and hydrogen peroxide contents. The reduction of MDA and H2O2 content in the presence of multi-walled carbon nanotubes (500 mg kg-1) and SNP were seen too. The physiological parameters improved in the presence of appropriate concentrations multi-wall carbon nanotubes (500 mg kg-1). This superiority was more evident when nanoparticles and SNP were used together.
