Анотация: Seeds of tomato were soaked in double distilled water (control) or sodium nitroprusside (SNP; 10-8, 10-7, 10-6, 10-5, 10-4, 10-3, 10-2, 10-1 or 1.0 M) a nitric oxide (NO) donor, for 8 h. SNP significantly affected the seed germination, NR activity and seedling growth in a concentration dependent manner. The concentrations ranging from 10-8 to 10-5 M favored these parameters, whereas, the higher concentration of SNP (1M) showed an inhibitory effect. However, proline content and antioxidant enzyme exhibited an increase in response to 1M of SNP. It is concluded from the present investigation that nitric oxide acts as a stimulator at low concentrations whereas at higher concentration it acts as a stress inducer