[Objective] To illustrate the comparative effects of salt and alkali stresses on antioxidases of willow

and to provide scientific basis for willow breeding.[Methods] A willow cultivar Salix psammophila (Yanliu yihao) was used in this study. The stress conditions were simulated by five levels of salinities and alkalities with 14 days duration. The salinities were simulated by two neutral salts (NaCl and NaSO4) and alkalities were simulated by two alkaline salts (NaHCO3 and Na2CO3). The two neutral and alkaline salts were both mixed in the molar ratio of 9:1. The concentrations ranged from 0 to 200 mmol/L both for salt and alkali stress.[Results] Under alkali stress

the activities of superoxide dismutase (SOD)

peroxidase(POD) and CAT all presented a tendency of increasing at low concentration stress and then decreasing at high stress. The peak of SOD activity emerged when the willow was treated with 100 mmol/L

which was 1.48 times of the control's; the peak of POD and CAT activities emerged when it was treated with 150 mmol/L

which were 4.26 and 2.79 times of the control's values. Under alkali stress

the activities of SOD

POD and CAT all presented an increasing tendency. The peaks of SOD

POD and CAT activities all emerged at highest contrcentration of 200 mmol/L

they were 1.33

3.26 and 2.29 times of the control's corresponding values. The content of MDA of willow leaf was higher in alkali treatment than that in salt treatment. When the concentrations of neutral and alkaline salts were at 150 mmol/L

the difference of MDA content was biggest.[Conclusion] The alkali stress is different from salt stress

the alkali has stronger injury to willow than the salt stress has.