There has been increasing interest in the use of engineered nanoparticles in agricultural science. Recent research has revealed that nanoparticles have both negative and positive impacts on plant growth performance. The present study is motivated by conflicting results from previous researches on the probable impact of engineered nanoparticles on crop growth. Hence, a greenhouse experiment was conducted to investigate the possible impacts of nano titanium dioxide (n-TiO ) (500, 1000 and 2000 mg kg-1) and nitric oxide (NO) (100 μM SNP as NO donor) on growth, physiological and photosynthetic parameters of barley seedlings (at the 30th stage of Zadoks growth scale) under salinity stress. Salt-stressed plants showed stunted growth, decreased shoot and root lengths, less chlorophyll and lower photosynthesis stomatal conductance (Gs), but increased proline and antioxidant enzymes activity in leaf tissue. The n-TiO promoted growth and photosynthetic performance of barley plants under salt stress. Sodium nitroprusside (SNP) supplied with n-TiO counteracted deleterious effects of salinity on growth parameters. Enhanced superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activities with less malondialdehyde (MDA) were observed in presence of 100 μM SNP. It is suggested that engineered nanoparticles and SNP-induced salt tolerance in barley are likely associated with increases in some antioxidant enzyme activities. Moreover, MDA and hydrogen peroxide (H2O2) concentrations in the shoot of barley were alleviated by n-TiO and SNP application. Taken together, based on all these data it can be concluded that n-TiO with employing NO donor in the form of SNP might be a promising approach in counteracting the adverse effects of salinity stress on barley growth.
