Study of the effect of salicylic acid application before and after wounding on growth, antioxidant defense, and rosmarinic acid production in Melissa officinalis

In this study, the effects of exogenous salicylic acid (SA) application at concentrations of ۱ and ۱.۵ mM, alone and in combination with mechanical wounding stress (applied before and after wounding), on growth, photosynthetic pigments, oxidative status, antioxidant enzyme activities, phenylalanine ammonia-lyase (PAL) activity, and the content of phenolic compounds and rosmarinic acid (RA) in lemon balm (Melissa officinalis L.) were investigated. The results revealed that SA alone enhanced shoot and root biomass and increased chlorophyll and carotenoid contents. Wounding alone reduced biomass, elevated H₂O₂ levels, lipid peroxidation (MDA), and lipoxygenase (LOX) activity; however, SA priming (before wounding) significantly mitigated these negative effects. Antioxidant enzyme activities (CAT, GPX, APX, GST, and SOD) increased in an intensity-dependent manner, with a shift toward non-enzymatic defense observed. The most important finding was the strong induction of PAL enzyme activity (۳-fold) and a significant increase in the content of phenolic compounds (۲.۶-fold) and RA (۵.۶-fold) in the combined W+SA treatment compared to the control. Overall, SA priming before wounding proved the most effective strategy for alleviating stress damage and maximizing RA production as a valuable secondary metabolite. These findings elucidate the mechanisms of SA-wounding signaling interactions in this medicinal plant and offer practical applications for enhancing pharmaceutical compound production under stress conditions.

کلیدواژه ها:

Priming ، Wound signaling ، Secondary metabolites ، Melissa officinalis ، Salicylic acid ، پرایمینگ ، سیگنالینگ زخم ، متابولیت ثانویه ، Melissa officinalis ، سالیسیلیک اسید