摘要：Levmus chinensis, which mainly grows in the high latitude area of northern China, is likely to be confronted with the local stresses of both freeze- thaw and saline-alkali. Previous reports have focused on a single stress, while the effects of the combined stress of freeze-thaw and saline-alkali on the grass, particularly on the important rhizome organ for adversity adaptation, are not documented; thus, knowledge of the relevant physiological response is inadequate. Therefore, this study was designed to characterize and explain the impact of the combined stress of saline-alkali and freeze-thaw on the activities of antioxidant enzymes, the content of osmotic adjustment substances and membrane peroxidation in L. chinensis. Samples were collected from five soil sites with different pH values for the freeze-thaw treatment in the laboratory (temperature gradient: 5, 0, -5,-10, -5, 0 and 109C). The resultshows that when the temperature dropped to subzero, the activities of antioxidant enzymes, as well as the content of the osmotic adjustment substances and malondialdehyde (MDA), increased. At the end of the freeze stage, the maximum of the contents of soluble sugar, proline and MDA was observed at t4 (-10C), while the antioxidant enzyme activities decreased significantly. The L. chinensis rhizome is sensitive to changes in ambient temperature, which could inhibit membrane lipid peroxidation through the activation of the antioxidant enzyme systems at 59C. Under saline-alkali stress, the changes described above helped to prevent membrane peroxidation and maintain normal osmotic adjustment in the rhizomes. Antioxidant enzyme activities and the content of osmotic regulators increased significantly under the combined stress. In conclusion, the L. chinensis rhizome could reduce the stress damage through the accumulation of antioxidant systems and cell permeation, and the combined stress was more harmful to the rhizome of L. chinensis than the single stressors.
