Abstract: 【Objective】The purpose of this paper is to clarify the protective effects of nitric oxide (NO) on seed germination, seedling growth and leaf oxidative damage in osmotic stress cucumber (Cucumis sativus L.).【Method】Under 25% (W•V-1) PEG-6000 stress condition, the effects of sodium nitroprusside (SNP, an exogenous nitric oxide donor) at the concentration of 0.1 and 0.5 mmol•L-1 on the germination, growth, leaf oxidative damage and protective enzymatic activities in cucumber seedlings were investigated.【Result】The significant effect on the alleviation of osmotic stress damage was observed in the treatment of 0.1 mmol•L-1 SNP. At this concentration, the seed germination rate, germination index and vigor index were increased by 18.89%, 86.03% and 3.02 times respectively, plant height, root length and fresh weight were increased by 1.15, 2.17 and 1.16 times respectively, proline content and activities of SOD, POD, CAT and APX in leaves were increased by 50.99%, 42.39%, 66.58%, 79.03% and 116.39% respectively, while malondialdehyde (MDA) content in leaves was decreased by 4.13 times.【Conclusion】The above results indicated that and dosage effect of exogenous nitric oxide donor (SNP) existed on the promotion of germination and alleviation of osmotic stress in cucumber seedlings, and better alleviation effect on osmotic stress damage was 0.1 mmol•L-1 SNP, which elevated the drought resistance of plants.

Key words: Cucumber, Seed germination, nitric oxide (NO), Osmotic stress, Oxidative damage