The effect of sodium nitroprusside (SNP) on functional, phytochemical and physiological characteristics of peppermint (Mentha piperita L.) under salinity stress

To investigate the effect of sodium nitroprusside (SNP) as an effective antioxidant and its optimal effect in reducing oxidative stress in peppermint under salinity stress, an experiment was conducted in 2021 in the Hormozgan University greenhouse in a completely randomized design with three replications. In this study, the effect of two levels of SNP as a source of nitric oxide (NO) release with concentrations of 0-, 0.1, and 0.2 mM sodium nitroprusside on the parameters of relative leaf water content, plant greenness, chlorophyll fluorescence, and active ingredients of peppermint under stress salinity was evaluated at concentrations (0, 25, 50, 75 and 100 mM) of sodium chloride solution (NaCl). The results showed that the effect of the interaction of sodium nitroprusside and salinity on the relative water content of leaves, plant greenness, and chlorophyll fluorescence was significant at a level of 1% probability. The highest relative leaf water content was observed in the application of 0.1 mM sodium nitroprusside in control (94.48%) and the lowest in the presence of 0.2 mM sodium nitroprusside in control (56.66%). The results of the mean comparison showed that at 100 mM salinity levels, the application of 0.2 mM sodium nitroprusside increased plant greenness and chlorophyll fluorescence of peppermint by 29.78% and 14.70%, respectively. Many of the active ingredients, including menthol, decreased with increasing salinity stress, while the highest amount of menthol (14.20) was observed in the 100 mM salinity treatment of 0.2 mM sodium nitroprusside. In general, the results show that the use of sodium nitroprusside increases the growth and secondary metabolites of peppermint under salinity stress.