| Chrysanthemum indicum L., a medicinally important member of the Asteraceae family, is valued for both ornamental and therapeutic uses. Methyl jasmonate (MeJA), a key signaling molecule, helps regulate its growth and defense responses. This study sought to refine callus induction protocols and assess how different MeJA concentrations (0, 50, 100, and 150 µM) influence various metabolic, biochemical, morpho-physiological and antioxidant traits in callus cultures of Chrysanthemum indicum L. Following the germination of Chrysanthemum indicum seeds, various explants were cultured on MS medium under different hormonal regimes and light conditions to optimize callus induction. The most effective response (96.66% callus formation) occurred with leaf explants under a 16 h light / 8 h dark photoperiod, using a combination of 2 mg L⁻¹ BAP and 2 mg L⁻¹ 2,4-D. This condition also minimized initiation time and significantly boosted biomass. The fresh biomass of callus treated with 100 µM MeJA (2.72 g) was 1.05 g higher than the control (1.67 g), and enhanced callus volume by approximately 2-fold compared to the control. At this concentration, chlorophyll a and b reached their highest levels, accompanied by elevated production of carotenoids, phenolics, flavonoids, and enhanced antioxidant activity. At 150 µM MeJA, the maximum carotenoid (3.30 mg g⁻¹ FW), phenolic (68.42 mg g⁻¹ FW), and flavonoid (46.19 mg g⁻¹ FW) levels were observed, along with a 33.79% rise in antioxidant potential relative to untreated controls. Additionally, MeJA treatment led to reduced malondialdehyde (MDA) levels, suggesting lower lipid peroxidation, as well as elevated proline and anthocyanin contents, indicative of improved oxidative stress tolerance. In summary, MeJA application, particularly at 100 and 150 µM, favorably influenced callus growth and enhanced secondary metabolite biosynthesis. These outcomes highlight MeJA's utility as an effective elicitor to improve the in vitro production of medicinal metabolites. |