Abstract: Taking Jinyun NO.5 cucumber（Cucumis sativus L.） as the test materials, the experiment was conducted to study the effects of different concentrations 5-aminolevulinic acid（5-ALA） on seed germination and seedling growth of cucumber under the condition of 20% PEG-6000 drought stress. The results showed that, drought environment seriously inhibited the germination of cucumber seeds, and different concentrations of 5-ALA can alleviate the effects of drought stress on cucumber seed germination. With the increase of 5-ALA concentration, the germination rate, germination index and vigor index of seeds first increased and then decreased. Among them, 0.5 mg/L is the best concentration. Drought environment inhibits the growth of cucumber seedlings. Appropriate concentration of 5-ALA can significantly increase the drought resistance of cucumber seedlings. At a concentration of 0.5 mg/L, the dry weight, strong seedling index, root activity, soluble sugar content, free proline content, total chlorophyll content and carotenoid content of cucumber seedlings respectively increased by 99.13%, 104.51%, 70.42%, 40.79%, 163.46%, 38.59%, 126.92% compared with the dry environment.

Key words: cucumber（Cucumis sativus L.）, 5-aminolevulinic acid, seed germination, drought stress