Vetiver grass (Chrysopogon zizanioides (L.) Roberty) is a perennial herb that has been widely cultivated for its phytoremediation potential, prevention of soil erosion and, in particularr, for production of aromatic essential oils. The aim of this research was to evaluate the efects of sodium nitroprusside (SNP) on morpho-physiological traits, essential oils content and composition of vetiver grass exposed to water defcit stress. Three irrigation levels (40%, 70%, and 100% available water) and foliar application of SNP (250 and 500 μM) were applied to six months plants under greenhouse conditions. the fndings indicated that water defcit reduced shoot and root growth, leaves chlorophyll, carotenoid and relative water content whereas, total phenol and favonoid content, electrolyte leakage, proline, antioxidant enzyme activity, and roots essential oils content increased with decreasing soil available water. SNP application ameliorateed adverse efects of water defcit stress by rising antioxidant capacity, proline, phenolic compounds and pigments accumulation as well as reducing electrolyte leakage, which was highly pronounced in 500 μM cobcentration. The highest shoot and root dry weight were obtained from SNP at 500 and 250 μM in the irrigation level of 100% available water, respectively. The maximum amount of phenol, total favonoids, essential oil percent (0.284%), proline, catalase, and peroxidase were observed in plants exposed to the 40% available water following treatment with 500 μM SNP. Heatmap results showed that the impact of SNP on vetiver grass is more signifcant under severer stress, while its efciency might decrease under no-stress condition. Therefore, applying water defcit stress and SNP would be a potantial tool for improving plant essential oils yield.
