Abstract: [Objective] To understand the effects of salt and alkali stress on seed germination and seedling growth of Sorghum sudanense. [Methods] With Sorghum sudanense seeds as experimental materials, one ultrapure water control group and three salt and alkali stress groups （NaCl, Na₂CO₃ and NaOH） were set up. Each group was set with 6 concentration gradients: the concentrations of the NaCl group were 50, 100, 150, 200, 250, and 300 mmol/L; the concentrations of the Na₂CO₃ group were 15, 25, 50, 75, 100, and 150 mmol/L; and the concentrations of the NaOH group were 5, 10, 15, 20, 25, and 30 mmol/L. Sorghum sudanense seeds were placed in a petri dish containing treatment solution （25 ℃ dark culture）, and the number of germination was recorded daily. At the end of the germination test, the root length, bud length, fresh weight and dry weight of the seeds were measured, and the seed germination rate, germination potential and germination index were calculated. According to the measured indicators, the critical values of salt and alkali stress of NaCl, Na₂CO₃ and NaOH on Sorghum sudanense seeds were calculated. [Results] When the NaCl concentration was greater than or equal to 100 mmol/L, the seed germination rate and germination potential were significantly （P<0.05） lower than those of the control group. When the concentration was greater than or equal to 50 mmol/L, the seedling bud length, root length, fresh weight and germination index were significantly （P<0.05） lower than those of the control group. When the concentration of Na₂CO₃ was greater than or equal to 75 mmol/L, Sorghum sudanense seeds did not germinate. When the concentration was higher than 15 mmol/L, the germination rate, germination index, bud length, root length and fresh weight were significantly （P<0.05） lower than those of the control group. Compared with the control group, there was no significant difference （P>0.05） in seed germination rate, germination potential, or dry weight among all concentration gradients of NaOH. The bud length and root length were significantly （P<0.05） lower than the control group at the concentration of 10 mmol/L. The fresh weight was significantly （P<0.05） lower than that of the control group at the concentration of 5 mmol/L. The critical concentrations of NaCl, Na₂CO₃ and NaOH for Sorghum sudanense seeds were 269.52, 49.18 and 124.76 mmol/L, respectively. The sensitivity of Sorghum sudanense seeds to salt and alkali was Na₂CO₃>NaOH>NaCl. [Conclusion] The effects of saline-alkali stress on the seed germination and seedling growth of Sorghum sudanense vary with salt types and concentrations. Among them, Na₂CO₃ has the strongest inhibitory effect, while NaCl has the weakest. Moreover, the seedling growth indices （especially fresh weight and root length） are more sensitive to saline-alkali stress than the germination indices （such as germination rate）.

Key words: salt stress, alkali stress, Sorghum sudanense, seed germination