Application of sodium nitroprusside and silicon on the enzyme activity of Solanum lycopersicum during vegetative growth

ABSTRACT One of the most deleterious abiotic stresses is the salinity stress, which causes inhibition of growth and development. Therefore, this investigation was conducted to evaluate the effects of sodium nitroprusside (SNP) and silicic acid (Si) on biochemical response of Solanum lycopersicum (cv. Isabella) under different salinity levels during vegetative stage. For this purpose, the seedlings were subjected to different salt stress levels (0, 25, 50, 100, and 150 mM) and supplemented with optimized concentration of silicon (Si) (0, and 2.5 mM of H4SiO4) and sodium nitroprusside (SNP) (0, and 100 µM) to assess variations in enzyme activity and biochemical properties of tomato plants during vegetative growth. Salt stress inhibited the chlorophyll and carotenoid contents of tomato plants. The antioxidant enzyme activities such as catalase (CAT) and superoxide dismutase (SOD) as well as the levels of osmolytes (proline, glycine betaine), malondialdehyde (MDA), and hydrogen peroxide (H2O2) increased in tomato plants due to high salinity. Furthermore, the exogenous use of SNP and Si to alleviate the effect of salinity on the plants increased the antioxidant enzyme activities and osmolyte levels compared to NaCl-treated plants. In addition, in the plants under salt stress, supplemented with SNP and Si, the contents of MDA and H2O2 decreased. Therefore, the exogenous use of Si and SNP led to protecting a tomato plant against oxidative damage induced by salt stress by stimulating synthesis of antioxidant enzyme. The findings indicated that, with the improvement in antioxidative defense system, pigment syntheses, and osmolyte accumulation, SNP and Si had the ability to alleviate adverse impact of high salinity on tomato plants.