Influence of L-Tryptophan and Melatonin on Germination of Onion and Leek Seeds at Different Temperatures

Abstract

In this study, the effects of pre-sowing L-Tryptophan and Melatonin treatments on germination of onion and leek seeds under different temperature conditions were investigated. Seeds were treated with 125, 250, 375 ppm L-Tryptophan and 5, 10, 25 uM Melatonin for 24 hours, then subjected to germination tests at optimum (21 ˚C) chilling stress (7 ˚C) and hot temperature (35˚C) conditions. Treated with distilled water seeds were considered as controls. Treatment of onion seeds with 125 ppm L-tryptophan had a significantly positive effect on final germination ratio at 7˚C while in leek seeds, the 5 µM concentration of melatonin had a significant effect on the germination index at the same temperature. In both Allium species, hormone treatments had no effect on mean germination time. These values decreased depending on the increase in temperature. The extreme level of high temperature burned certain percent of seedlings, while at low temperature, seedlings were not harmed by cold domination.