| Summary: | This study was carriedout with the objective to evaluate the effects of different concentrations of L-Tryptophanand Melatonin pretreatment on germination behavior of onion, leek, black carrot,and radish seeds exposed to saline stress. Seeds of samples were soaked for 24hours in distilled water, 50,100, 150 ppm L-tryptophan, and 1.5, 3, and 4.5 µMmelatoninsolutions at 20° C in darkness. Seeds were placed in Petri dishes and wateredto moisten the filter paper with different concentrations of NaCl (0, 150, 300or 450 mM). The experiment was planned in a completely randomized design withfour replications. Maximum germination percentage, germination index, time tocomplete 50% germination and mean germination time was measured at the end ofthe study. The results indicated that the effect of pre-treatment wassignificant on all studied traits in all species except for mean germinationtime for black carrot seeds. In addition, all germination parameters of seedswere delayed and decreased by salinity increasing from 0 mM to 450 mM NaCl. Overall,all doses of melatonin increased the maximum germination ratio and germinationindex values slightly under 300 mM NaCl stress conditions. In general, resultswhich obtained from all doses of melatonin were close to each other, whereasincreasing doses of L-tryptophan caused a negative effect in some cases.
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