Cyclic 3-hydroxymelatonin application improves chilling tolerance by regulating selected biochemical properties and antioxidative enzyme activities in pepper

One of the main melatonin metabolites in plants is cyclic 3-hydroxymelatonin (3-OHM), although its potential functions in plant life remain unclear. To understand the importance of 3-OHM in plants in terms of stress tolerance, we investigated whether tolerance to chilling stress could be increased during germination and emergence using exogenous 3-OHM applications in pepper. After being exposed to varying concentrations of 3-OHM for 24 h, pepper seeds were tested for germination and emergence under both optimum and chilling stress conditions. Applying 3-OHM prior to sowing had a positive effect on pepper seed germination and seedling emergence performance under chilling stress circumstances. Concentrations of 10 and 50 μM 3-OHM were determined to be the most effective 3-OHM concentrations, therefore the germination and emergence percentages and rates increased in contrast to control treatments. 3-OHM treatments raised the activity of the enzymes peroxidase, catalase and superoxide dismutase while decreasing the quantities of reactive chemicals such as hydrogen peroxide and thiobarbituric acid in seedlings. Furthermore, treatments had a positive effect on seedling proline content, root length, vigor index and chlorophyl content. In conclusion, increased antioxidant enzyme levels significantly reduce lipid peroxidation in tissues, consequently boosting pepper seed germination and seedling emergence performance.