Abstract: The effects of different concentrations of exogenous 5-aminolevulinic acid on seed germination and seedling growth ofmung bean under salt stress were studied by using mung bean as test material and 150 mg/L concentration NaCl as simulated salt stress. The results showed that different concentrations of 5-aminolevulinic acid promoted the germination and seedling growth of mung bean at low concentration and inhibited at high concentration under NaCl stress, the germination rate and germination potential of green beans increased first and then decreased with the increase of treatment concentration, reaching the highest concentration of 50 mg/L and 150 mg/L respectively. Exogenous 5-aminolevulinic acid played a significant inhibitory role when the concentration reached 250 mg/L. The leaf area and root length of mung bean at seedling stage increased first and then decreased with the increase of treatment concentration. When the treatment concentration reached 100 mg/L, both reached the maximum value. With the increase of 5-aminolevulinic acid concentration, malondialdehyde （MDA） decreased at first and then increased, and reached the lowest when the treatment concentration reached 150 mg/L. The content of proline and soluble sugar increased first and then decreased, and reached the highest when the treatment concentration reached 150 mg/L and 100 mg/L, respectively. The results showed that 5-aminolevulinic acid had a significant effect on the stress resistance of mung bean seedlings. The optimal concentration of exogenous 5-aminolevulinic acid on mung bean germination under NaCl stress was about 100 mg/L, and the optimal concentration for seedling growth of mung bean under NaCl stress was 150 mg/L.

Key words: 5-aminolevulinic acid, salt stress, mung bean, stress resistance