Sodium Nitroprusside and Putrescine Mitigate PEG-Induced Drought Stress in Seedlings of Solanum lycopersicum

Crop plants all over the world face an array of environmental threats among which drought is found to be the most deleterious. The present investigation was carried to test the efficacy of exogenously supplemented sodium nitroprusside (SNP), a nitric oxide donor, and polyamine (PA) putrescine (PUT) in mitigating the effects of polyethylene glycol (PEG)-imposed drought stress in in vitro grown seedlings of Solanum lycopersicum. PEG treatments at different concentrations (1, 2, 5, 10, and 15%) were assessed for their impact on plant growth parameters based on which 10% PEG was chosen as effective drought treatment. Varying concentrations of SNP (100, 150, and 200 mu M) and PUT (0.1, 0.3, and 0.5 mM) at different combinations were studied for their mitigating effects. The results revealed that among the combinations tested, SNP (150 mu M) + PUT (0.3 mM) resulted in effective mitigation of drought stress in S. lycopersicum seedlings. SNP and PUT supplementation enhanced the growth parameters such as shoot and root length and plant fresh weight (FW). Further, the relative water content (RWC), chlorophyll, and proline contents were significantly enhanced in the experimental plants as compared to the control. Effective reduction in the malondialdehyde (MDA) and hydrogen peroxide (H2O2), a significant increase in the antioxidant enzymes, and the transcriptional level upregulation of antioxidant genes and drought-responsive genes were observed in the treated plants as compared to the control. These results suggest that exogenous supplementation of SNP and PUT has a positive influence on alleviating the drought stress in S. lycopersicum.