Magnesium Oxide Nanoparticles Improved Drought Resilience in L. through Lifting Antioxidant Level, Redox Balancing, and Improving Photosynthetic Efficiency.

Water scarcity has become challenging and has greatly impacted crop production globally. This study focused on adverse effects of drought on a delicate vegetable crop L. which is also used in spices worldwide. Furthermore, the role of magnesium oxide nanoparticles (MgONPs) in improving drought resilience in was also analyzed. For this, a two factorial pot experiment was designed in a completely randomized fashion with five replicates. For drought, the field capacity of stressed pots was maintained at below 40%. MgONPs were foliar sprayed using a manual hand sprayer at 300 mg L. Meanwhile, for comparative analysis, precursor molecules used for synthesis of MgONPs (i.e., MgSO) were also applied via a foliar spray at the same level. Results showed that drought severely reduced growth (shoot length; 17%, root length; 34%), whole plant fresh (34%) and dry (23%) weights, photosynthetic pigments (total chlorophyll; 37%), and chlorophyll fluorescence and performance index (74%). It also reduced photosynthesis rate (56%), transpiration rate (48%), and stomatal conductance (56%), whereas drought stress elevated the level of stress markers (relative membrane permeability; 43%, malondialdehyde; 32% and HO; 34%) and antioxidants (catalase; 26%, superoxide dismutase; 81%, peroxidase; >2 folds). Total phenolics and flavonoids were also increased by 23 and 51% in drought stressed plants. On the other side, MgSO and MgONPs successfully mitigated harsh effects of drought, but the MgONPs were more efficient in improving drought resilience of MgONPs improved photosynthetic pigments, chlorophyll fluorescence, gas exchange attributes, antioxidant defense, and ultimately growth of in both control and drought conditions. These findings suggest that MgONPs can potentially be used for improving drought resilience in crop plants.