The cultivar Dongnong 425 was 98.5 cm in plant heignt and about 140 days in growing period. The active accumulated temperature above 10°C in the whole growth season demand of the cultivar was 2 700°C. The experiment was laid out in Completely Random Design (CRD) with three replications for each treatment. Plump seeds were selected and sterilized with 10% sodium hypochlorite for 25 min, then washed 3 times with distilled water. The seeds were soaked with 0 (distilled water), 5, 15, 30, and 45 mmol • L-1 proline for two days at (30±1)°C. Then, 100 seeds from each proline-soaking treatment were placed on Petri dishes with 12 cm diameter on two layers of filter paper containing 25 mL 100 mmol • L-1 sodium chloride solution, compared with 25 mL distilled water control. To avoid artificial influence on seed germination and maintain the salt concentration