The Effects of Seed Treatment with Melatonin on Germination and Emergence Performance of Pepper Seeds under Chilling Stress

Melatonin was first isolated from bovine pineal gland more than half a century ago as an important animal hormone and since then it was proved to be present in almost all forms of life including eukaryotic unicells, prokaryotes, fungi, algae, animals and plants. In this study, the effects of pre-sowing seed treatment with melatonin on germination and emergence performance of pepper seeds under chilling conditions were investigated. Seeds were immersed in 0 (distilled water), 1, 5, 10 or 25 mu M melatonin solutions for 24 hours after which they were dried for one day and subjected to germination and emergence tests at optimum (25 degrees C) and chilling stress (15 degrees C) conditions. Untreated (dry) seeds were used as a control. Exogenous melatonin treatment promoted pepper seed germination and emergence under chilling conditions. Treatment of seeds with melatonin especially in 1 or 5 mu M concentrations significantly improved germination and emergence percentage whereas control seeds and seeds treated with water exhibited the lowest germination and emergence performance. Melatonin application also reduced the MDA and H2O2 contents and elevated SOD and CAT enzyme activities. The improvement in germination and emergence performance of pepper under chilling stress conditions following melatonin treatment may therefore be due to reduced lipid peroxidation and elevated activities of antioxidant enzymes.