Abstract: Drought is one of the most serious environmental factors which affect shrubs growth and limiting shrubs production,even can cause the plant to irreversible injury or even death. Minqin County is located at the eastern section of east Hexi Corridor,Gansu Province,China. It is one of the most arid regions in China for its east,west,and north was surrounded by Tengger Desert and Badain Jaran Desert. Desert shrubs are the most adaptable plant and play an important role in ecological construction of Minqin because of the actions on soil conservation and soil improvement,such as masking the surface,holding the soil,reducing evaporation,increases organic matter,improve soil structure. In this paper,four shrubs Lespedeza bicolor,Nitraria tangutorum,Haloxylon ammodendron and Caragana Korshinskii,have been selected to study their physiological response properties and ecological principle under drought conditions. And drought resistance of these shrubs has been evaluated with a view to Minqin artificial vegetation construction,restoration of ecology and environment and development of grassland animal husbandry. The main results are as follows:Severe drought stress significantly affected the growth of four kinds of shrub,total growth of Lespedeza bicolor in 15 days decreased from 36.31 mm to 7.28 mm (P<0.01). Leaf area of Haloxylon ammodendron,respectively 0.82 times and 0.66 times of the controls,was the smallest decline in four shrubs under moderate and severe drought stress,while leaf area of Lespedeza bicolor decreased to half the level of control. Relative water content of Lespedeza bicolor was also decreased by 9.20% and 38.33%(P<0.05). Cell membrane permeability of Nitraria tangutorum and Haloxylon ammodendron were increased slightly to 1.98 and 2.01,while that of Lespedeza bicolor and Caragana korshinskii were increased to 6.9 and 6.67(P<0.05) under severe drought stress. Osmotic adjustment substance such as proline and soluble sugar in the leaves of four shrubs showed different degrees of growth trend under different drought stress. According to the results of drought resistance evaluation using fuzzy membership function in 4 shrubs were as below:Nitraria tangutorum > Haloxylon ammodendron > Caragana korshinskii > Lespedeza bicolor.

Key words: shrub, water stress, drought resistance, Minqin