| In this paper ,the desert plant Tamarix L. in the lower reaches of Tarim River were studied . Combining the experimental plots with pot experiment of Kaerdayi cross section in the lower of reaches of Tarim River . Under natural drought conditions, the Study on System of Tamarix hispida's photosynthesis and water physiological characteristics and drought physiology adaptation. To disclosure the desert species Tamarix L's tolerate aridity limit and drought resisting machine ,this will provide the theory basis for researching the diversity of approach of drought defying in plants. Meanwhile, It's so significant for ecological restoration and economic construction in the area of Tarim River.Indicating that, 1.In the lower reaches of Tarim River ,the Tamarix hispida's Pn daily variation appeared as single peak, the Pn reached its maximum value at 11 o'clock in the morning ,about 28.128,μmol·mg-2·s-1.With the declining of ground water level , Tamarix hispida's Pn also decreased. When the ground water level declined about 8.0m, Tamarix L. could also hold out the stable photosynthesis. In different seasons, Tamarix hispida's Pn daily variation fluctuated differently, the value of August >June>October. And the maximum value appeared in different time. During the pot experiment, with soil relative moisture content decreased, Tamarix hispida's Pn and Cs daily variations were also declined. Accounting that photosynthesis decreased with the drought were mainly caused by stomatal aperture diminished under the arid condition.2. In the lower reaches of Tarim River, the Tamarix hispida's E daily variation fluctuated in a single peak, from 1pm to 5pm the transpiration was very strongly, WUE daily variation also appeared as single peak, the appearance of maximum was at 9am,about 4.513 mmolCO2·mol- 1H2O In the morning, the WUE was obviously higher than afternoon. With ground water level decreased, E showed a decreasing tendency, but the WUE. Oppositely, under the most drought condition, the E samples were higher than B and C ones in the noon and afternoon. In different seasons, Tamarix hispida's Pn daily variation appeared that transpiration intensely in the august. But in the June and October, the transpiration became lower, there was no significant discrepancy within them. Because of the high temperature and intensely lighting, WUE of June became higher than the august. WUE of august was lower than June, especially declined obviously after midday. During pot experiment, with water stress aggravation, the E and WUE were also declined.3. In the lower reaches of Tarim River, along with groundwater level decreased, the soluble sugar, Pro and dissolvable protein's contents of Tamarix hispida were increased. Especially the level was about 8m, MDA enhanced obviously. In October, the contents of soluble sugar, Pro and MDA were all higher than the August , the contents of June were lower than the August. The dissolvable protein contents'total level of June was higher than August, The total level of October was lower than the August. In the course of pot experiment, along with the water stress aggravation, soluble sugar, Pro and dissolvable protein's contents of Tamarix hispida were increased. Meanwhile, MDA and Plasmalemma damage degrees were gradually improved. When the soil relative water content was about 10%, Plasmalemma damage degrees achieve to the maximum value was about 16.91%,Indicating that MDA content's improvement were not bring the deadliness damage. The early sign of water stress could stimulate Tamarix ramosissima activity of protective enzymes increasing, and also could contain high enzyme activity during the late period. Following that, it could delete the active oxygen ,decrease the Plasmalemma harm degrees.
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