Abstract:Tomato seedling with 6-8 leaves was used to investigate impact of nitric oxide (NO) and sucrose on oxidative damage to young tomato leaves under NaCl stress. Sodium nitropresside (SNP) was used as NO donor. The tomato seedlings were grouped and then sprayed on surface of leaves with solutions of distilled water, NaCl, SNP, sucrose and SNP+sucrose (1∶1). After spraying 36h, the leaves were subjected to NaCl stress at 100 mmol/L for 24h, 48h and 72h respectively. The detail treatments as follows: A. CK(distilled water)；B. 100 mmol/L NaCl；C. 0.1 mmol/L SNP+100 mmol/L NaCl；D. 0.1 mmol/L SNP+ 1.0mmol/Lsucrose +100 mmol/L NaCl； E. 1.0 mmol/Lsucrose+100 mmol/L NaCl. The results indicated that there were protective function to tomato seedling leaves from NaCl oxidative damage when applications of SNP, sucrose and their mix solutions. However, the treatment-D showed a much better protective impact than the treatments of C and E as it could significantly increase activities of antioxidant enzymes (including SOD，CAT，POD，APX and GR) and content of proline，while largely decrease MDA content in tomato seedling leaves under salt stress. Moreover, the effect of salt stress on the peroxidase enzyme expression in tomato leaves was further analyzed by using polyacrylamide concentration gradient gel electrophoresis technique. The results showed that salt stress could inhibit the expression of small molecule POD isoenzymes. The mix solution of SNP and sucrose could largely promote POD isoenzyme activity and protective them from hydrolyzation than single application of either SNP or sucrose solutions. Irrespective of solution, the POD isoenzymes expression was higher at 24h than 48h salt stress. The mix solution of SNP and sucrose could have a big potential for reduction of oxidative damage to tomato seedling leaves under salt stress.