Physiological and phytochemical responses of lemon balm ( <i>Melissa officinalis</i> L.) to salicylic acid and cycocel under water stress conditions

Abstract The global expansion of drought stress, a major consequence of climate change, is adversely affecting crop production and resistance. This study aimed to investigate the efficacy of salicylic acid (SA) and cycocel (CCC) in mitigating the adverse effects on lemon balm ( Melissa officinalis L.). The results revealed that the essential oil (EO) yield and percentage were mostly enhanced by 37% and 33%, respectively, under mild drought stress, indicating the plant's adaptive mechanism to optimize EO production under moderate stress conditions. Proline content also increased, reaching ∼2.45 µg g −1 fresh wt. under severe drought with foliar application, representing a 40% increase compared with untreated plants. Similarly, the enzymatic activities of catalase and superoxide dismutase were enhanced by 26% and 30%, respectively, under the same conditions. Overall, our results suggest that SA and CCC are effective plant growth regulators for lemon balm cultivation, particularly in arid areas.