Effect of selenium application methods on growth, water productivity and essential oil of peppermint (Mentha piperata L.) under drought stress

BACKGROUND: Selenium (Se) is one of the beneficial elements for plants and can enhance the antioxidant capacity and tolerance of plants against the adverse effects of drought stress. This research was conducted to investigate the effects of applying different forms of selenium in mitigating drought stress on the growth characteristics, water use efficiency, and essential oil percentage of peppermint (Mentha × piperita). Plants were subjected to two irrigation regimes (100% and 50% of crop evapotranspiration [ETc⦌) and selenium was applied at four levels: no application (control), mixing with irrigation water at a concentration of 5 mg L⁻¹ sodium selenate, foliar spraying of 5 mg L⁻¹ sodium selenate before imposing drought stress, and foliar spraying of 5 mg L⁻¹ sodium selenate after imposing drought stress on peppermint plants. RESULTS: The results showed that increasing drought severity significantly reduced biomass, root weight, photosynthetic pigments, essential oil percentage and relative water content, but increased water productivity, total phenol, electrolyte leakage, and antioxidant activity. Application of selenium, particularly as a foliar spray before drought, effectively mitigated the negative impacts of drought stress, leading to notable increases in shoot fresh and dry weight, essential oil yield, water productivity, pigment concentrations, relative water content, total phenol, electrolyte leakage, and antioxidant activity. CONCLUSIONS: These findings demonstrate that low-concentration selenium application is a practical strategy to improve drought tolerance and productivity in peppermint, and suggest foliar spraying of selenium prior to stress as the most effective treatment for optimizing growth and essential oil yield under water-limited conditions.