The mechanisms of melatonin in low-temperature stress tolerance in postharvest fruits and vegetables

Low-temperature storage of fresh fruits and vegetables, especially below the critical storage temperatures, leads to chilling injury that makes the produce unsuitable for market use. Postharvest application of melatonin for chilling injury alleviation in fruits and vegetables is an alternative preventive measure for the longer persistence of fresh produce on the market. This review classified the mechanisms involved in melatonin-mediated chilling tolerance into physiological, biochemical (sugar metabolism, organic acids, lignification and respiratory modulation, ripening, senescence, membrane structure, maintenance of the antioxidant system, endogenous proline, endogenous polyamine, γ-amino butyric acid shunt pathway, and modulation of energy status), and hormonal (ethylene, indole acetic acid, jasmonic acid, and abscisic acid regulation) pathways. Melatonin acted via several mechanisms, including antioxidant activity elevation, induction of antioxidant enzymes, gene expression regulation, gamma-aminobutyric acid shunt pathway, induction of stress-tolerant proteins, and cell membrane stabilization. However, dose and duration of exposure optimization, along with alternative means for mass production of melatonin, is required to promote trails.