Effect of exogenous nitric oxide donor on oxidative stress in basil (ocimum basilicum l.) under drought stress

This study investigated the efficiency of sodium nitroprusside (SNP) foliar spraying on basil (Ocimum basilucum) growth and oxidative stress alleviation under drought conditions. Basil plant subjected to four water levels (100, 75, 50 and 25% FC), at the same time leaves were sprayed with 100, 150 and 250 μM SNP. The results demonstrate that basil growth significantly decreased under drought stress, while SNP spraying, with all studied concentrations, significantly enhanced plant growth under drought conditions. Out of three SNP concentration tested, 150 μM proved to be the optimal treatment for ameliorating drought stress. Chlorophyll a, chlorophyll b and carotenoids content increased under drought conditions. Application of SNP at all studied treatments significantly improved chlorophyll a and carotenoid content mainly under moderate and severe drought condition (50, 25% FC). Proline concentration in the basil leaves significantly decreased under drought condition while SNP application alleviated osmatic stress. As indicators of drought stress, H2O2 and MDA content increased. SNP application alleviate drought stress by reducing H2O2 and MDA content. The beneficial effect of SNP was apparent in plants defensive state, where the concentration of ascorbic acid, oxidized glutathione and the activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) showed higher levels compered to untreated stressed control. Under all drought levels, the most pronounced improvement achieved for SOD activity (3 folds) by applying 250 µM SNP, for APX activity (24 folds) at150 µM SNP and for GR activity (2 folds) at 100 µM higher than untreated stressed plants. Therefore, foliar usage of SNP at 100, 150 and 250 µM might be suggested as an efficient way for enhancing basil tolerance to drought stress.