Effect of Methyl Jasmonate on the Growth, Antioxidant Potential, and Phenolic Compound Synthesis of Arnica montana L. In Vitro Shoots

Arnica montana L. is a valuable medicinal plant with strong anti-inflammatory properties attributed to its high levels of antioxidants and specific metabolites. The species is endemic to Europe, and its natural populations are threatened by habitat disturbance and poor management. In vitro plant cultures are an alternative method for rapid plant multiplication and the controlled synthesis of biologically active substances. Elicitation is a common strategy for inducing physiological changes and defense responses in plants, thereby increasing their antioxidant potential and the synthesis of specialized metabolites. Methyl jasmonate, a plant growth regulator involved in the modulation of plant growth and development at morphological and molecular levels, has gained increasing attention as an elicitor. In the present study, three concentrations of MeJA (50, 100, and 200 μM) were applied for 3 and 7 days to evaluate their effects on growth, antioxidant capacity, and accumulation of caffeoylquinic acids in in vitro shoots of arnica. Seven-day MeJA treatment reduced growth parameters and was accompanied by increased activities of antioxidant enzymes SOD and APX, as well as elevated levels of water-soluble antioxidants, which correlated with the enhanced accumulation of caffeoylquinic acids, total phenolics, and flavonoids. The results demonstrate that MeJA affected shoot growth and antioxidant potential of A. montana, with concentration and treatment duration playing a critical role in response magnitude.