2-hydroxymelatonin (2-OHM), a major melatonin metabolite, confers multiple stress tolerance in pepper at seed germination stage

Abstract

Besides affecting or regulating several crucial processes in plants’ growth and development, melatonin is also highly effective at reducing the oxidative damage induced by various abiotic stressors and therefore it is regarded as a new master plant hormone. The interaction of melatonin with several oxygenated compounds results in the formation of various metabolites that also exhibit melatonin-like functions. Although 2-hydroxymelatonin (2-OHM) is one of the principal melatonin metabolites found in plants, its possible roles in plant life are yet to be fully revealed. This study investigated the impact of 2-OHM treatment on pepper seed germination and seedling growth under various abiotic stress conditions. Pepper seeds treated with 50 µM 2-OHM were subjected to germination and emergence tests under chilling, salt, and water stress conditions. The results demonstrated that 2-OHM treatment significantly enhanced seed germination and seedling emergence performance compared to untreated seeds under stress conditions. The 2-OHM-treatemant resulted in higher final seed germination (FGP) and seedling emergence percentage (FEP) and root length under chilling and water stress conditions. Exogenously applied 2-OHM also significantly shortened the seed germination and emergence periods under chilling conditions as indicated by higher mean germination (MGT) and emergence rates (MET). Additionally, the 2-OHM treatment improved root length, FEP and MET under salt stress. In general, the 2-OHM treatment effectively reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels while increasing proline content and amplifying the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX) under all stress conditions. In conclusion, the 2-OHM treatment significantly improved seed germination and seedling performance and enhanced stress resilience in pepper at germination stage. This study highlights the potential of 2-OHM as an effective natural compound to enhance crop productivity and alleviate the adverse effects of abiotic stressors in agricultural practices. Future experiments will also assist in elucidation of 2-OHM intervened stress mitigation procedure in pepper.