Abstract:We studied the effects of salt-alkaline mixed stress on seeds germination, seedlings growth and leaf physiological characteristics of stress-resistance for the physiological response of a new naked oat(Avena nude) cultivar ‘Dingyou No 6’ to complex saline-alkali stress. A.nudeseeds and seedlings were cultivated in sands with different complex saline-alkali solution addition according to soil salinity composition of the planting areas. Germination rate, germination index, vigor index of seeds, water content and dry weight of seedlings were significantly decreased, while the contents of superoxide anion, hydrogen peroxide and malondialdehyde and relative plasma membrane permeability in leaves were increased evidently with increasing of the complex saline-alkaline stress. The complex saline-alkaline stress increased significantly Na+ contents, but reduced K+ contents and K+/Na+. The activities of plasma membrane H+-ATPase, peroxidase, ascorbate peroxidase and soluble protein content in leaves of the seedlings exhibited a humped-curve, while superoxide dismutase activities and the contents of glutathione, organic acid and proline were significantly increased. Catalase activity and ascorbic acid content were decreased evidently, free amino acid content first decreased and then increased, and soluble sugar content demonstrated a rose at first, and then dropped at last rose again. The imbalance of active oxygen metabolism and the disturbance of Na+ and K+ homeostasis in leaves resulted in the inhibition of naked oat seedlings growth, and the organic acid and proline are two possible osmotic adjusting substances of naked oats that are adapted to complex salt-alkaline stress.