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