Green-synthesized magnesium oxide nanoparticles enhance drought tolerance in cumin (Cuminum cyminum L.) by improving germination, photosynthetic efficiency, and biochemical defense mechanisms

One of the serious abiotic limitations that reduces the productivity of cumin (Cuminum cyminum L.) is drought stress. In this case, magnesium oxide nanoparticles (MgO-NPs) were prepared through a green synthesis pathway using rose petal extract and assessed to determine their possible application in repairing the drought effects in cumin. The DLS, FTIR, and TGA methods were used to characterize the synthesized nanoparticles. An assay of seed germination and a greenhouse experiment involving drought stress conditions (30% field capacity) showed that MgO-NPs increased the rate of germination, seedling growth, and biomass production significantly. Chlorophyll content and photosynthetic parameters (Fv/Fm, SPAD, and stomatal conductance) were restored by MgO-NPs during drought. Biochemical analyses revealed that there were higher levels of osmolytes (proline, glycine betaine, and soluble sugars) and lower levels of H2O2, MDA, and EL in drought-stressed plants that were treated with MgO-NPs. The activities of antioxidant enzymes (CAT, APX, PPO) were also moderately increased, which proves the protective properties of MgO-NPs against oxidative damage. The use of correlation heatmaps and PCA established a high dependency between MgO-NP treatment and enhanced physiological and biochemical characteristics. These results imply that MgO nanoparticles synthesized using a green method can be used to promote drought tolerance in cumin by developing several protective mechanisms, as the use of green-synthesized nanoparticles is sustainable in promoting crop performance under water-limiting conditions.