The role of magnesium oxide foliar sprays in enhancing mint (Mentha crispa L.) tolerance to cadmium stress

This study investigates using magnesium foliar spray to enhance mint plants' growth and physiological performance under cadmium toxicity. It examines the effects of foliar application of magnesium oxide (40 mg L-1), in both nano and bulk forms, on mint plants exposed to cadmium stress (60 mg kg(-1) soil). Cadmium stress reduced root growth and activity, plant biomass (32%), leaf hydration (19%), chlorophyll levels (27%), magnesium content (51%), and essential oil yield (35%), while increasing oxidative and osmotic stress in leaf tissues. Foliar application of magnesium increased root growth (32%), plant biomass, essential oil production (17%), leaf area (24%), chlorophyll content (10%), soluble sugar synthesis (33%), and antioxidant enzyme activity, and reduced lipid peroxidation and osmotic stress. Although the nano form of magnesium enhanced magnesium absorption, its impact on growth and physiological performance was not significantly different from the bulk form. Therefore, foliar application of both forms improves plants' ability to withstand cadmium toxicity. However, the study is limited by its focus on a single plant species and specific environmental conditions, which may affect the generalizability of the results. The long-term sustainability of such treatments could provide a more comprehensive understanding of magnesium's role in mitigating heavy metal stress in plants.