Nitric oxide mediated growth enhancement of tomato under salinity stress

Salinity is a major problem for agricultural production throughout the world significantly limiting crop production. Here, we evaluated the effect of different concentrations of nitric oxide (NO) growth and development of five different tomato cultivars under salt stress induced by different concentrations of sodium chloride (NaCl). Results showed that germination was significantly reduced by the salt-stress treatments in a dose-dependent manner, where germination was significantly reduced by 75 mM NaCl but completely suppressed by 100 mM NaCl. Pre-treatment of seeds with 0.001 mM sodium nitroprusside (SNP) as a NO donor for 8 h not only accelerated the germination rate but also significantly improved the growth of seedlings under salt stress induced by 50 mM NaCl as compared to the salt-stressed plants not treated with SNP. Real-time PCR analysis showed that SNP treatment decreased the expression of antioxidant gene SlGRX1 after 6 and 12 h of the treatment but increased after 24 and 48 h. On the other hand, the expression of SlAPX1 was reduced at all time points, indicating a reactive oxygen species (ROS)-scavenging effect of the SNP treatment via GRX1 transcript accumulation. This suggests that NO plays a vital role in seed germination and early plant development. It is, therefore, concluded that exogenous NO treatment of tomato seeds can improve seed germination and plant growth under saline conditions.