Methyl jasmonate (MeJA): A multifaceted regulator of growth, stress resilience, floral quality, and postharvest longevity in ornamental horticulture – A conceptual and functional review

Methyl jasmonate (MeJA), a volatile derivative of jasmonic acid, has emerged as a versatile phytohormone elicitor in ornamental horticulture, addressing key challenges in growth regulation, stress tolerance, secondary metabolite production, floral quality enhancement, and postharvest preservation. This review synthesizes multidisciplinary evidence from physiological, molecular, and omics studies to provide a conceptual and functional framework for MeJA's actions, emphasizing mechanisms, species-specific responses across cut flowers, loose flowers, and potted ornamentals, dosage effects, and practical constraints. MeJA's biosynthesis via the octadecanoid pathway, perception through the Coronatine Insensitive 1 ( COI1 )–Jasmonate ZIM-domain ( JAZ )– MYC2 transcription factor signaling module, and multifaceted applications in high-value ornamental crops are explored. Exogenous MeJA confers broad-spectrum abiotic stress resilience by boosting antioxidants, osmolytes, and barrier fortifications, but its efficacy varies by product type: in cut flowers like Rosa, it primarily extends vase life; in loose flowers like Lilium, it enhances scent and color; and in potted ornamentals like Begonia, it promotes compact architecture. Against biotic threats, MeJA primes direct defenses (e.g., phenolics, phytoalexins) and indirect volatile-mediated attraction of natural enemies. However, physiological costs include potential ethylene sensitivity in some species, leading to accelerated senescence at high doses. It modulates plant architecture, enhances floral traits, and differentially regulates storage organ formation in geophytes. As a potent elicitor, MeJA amplifies pharmaceutically valuable compounds, enabling dual-purpose cultivation. Postharvest applications extend vase life and preserve quality, with synergies in combinations. Hormone crosstalk reveals synergies and antagonisms, positioning MeJA as a cornerstone for sustainable production. Future directions emphasize optimized formulations, omics-guided breeding, and addressing limitations like phytotoxicity risks to realize MeJA's full potential in a conceptual framework that integrates category-specific responses and growth-defense compromises.