Methyl Jasmonate Mitigates Drought Stress in Purple Basil by Enhancing Photosynthesis and Secondary Metabolism

Drought significantly reduces crop yield, highlighting the need for effective strategies to combat its effects. Phytohormones like methyl jasmonate (MJ) offer promise in enhancing plant stress tolerance by bolstering defense mechanisms. Purple basil (Ocimum basilicum L.), a valuable vegetable renowned for its bioactive compounds, faces substantial damage from water scarcity. Hence, our study focuses on evaluating the efficacy of MJ application in alleviating drought stress in purple basil. For this, purple basil plants were grown in a completely randomized design in a 3 × 2 (irrigation frequencies × MJ treatments) factorial scheme, with seven replications. The growth, gas exchanges, chlorophyll fluorescence, photosynthetic pigments, relative water content, electrolyte leakage, sugars, phenolic compounds, and anthocyanins were determined. MJ treatment alleviated the deleterious effects of drought stress on growth, relative water content, and gas exchanges but decreased the chlorophyll fluorescence parameters of the plants. Moreover, MJ increased the contents of chlorophyll a, b, carotenoids, sugars, phenolic compounds, and anthocyanins, while reduced electrolyte leakage. Our findings indicate that MJ triggered the production of osmolytes and secondary metabolites, boosting antioxidant defense and photoprotection, while also mitigating electrolyte leakage and sustaining water balance, photosynthesis, and plant growth. In summary, MJ effectively relieved drought stress in purple basil by enhancing its photosynthetic capacity, secondary metabolism, and overall quality attributes.