| Using Chinese seabuckthorn widely growing in Loess Plateau as materials , this paper mainly deals with the drought-resistant mechanism and water condition and productivity of the seabuckthorn under different habitats .This experiment included indoors and outdoors .we studied the protective function of exogenous anti-oxidation matter including Vc> VE and $ -carotene on cell membrane of seabuckthorn leaf under PEG osmotic stress and observed stomata apertures of seabuckthorn with scanning electron microscopy, so partly discovered the causes of the drought-resistant and drought-avoidance seabuckthorn .we also studied water physiological ecology characteristics of seabuckthorn under the 5 kinds of typical habitats of semiarid loess hilly region in the north of shaanxi, Loess Plateau. The typical habitats are classified that hill-top, sunny, shade, semi-shade, semi-sunny hillside. During the whole growth season ,Main methods studied are the collected data of transpiration rate, diffuse resistance, relative water content and water-hold capacity ,while analyzing the relationships of these characteristics and environment factors and surveying their growth conditions and biomass .l.The protective function of exogenous anti-oxidation matter including V^ VE and P -carotene on cell membrane of. seabuckthorn leaf under PEG osmotic stress was analyzed. The results showed that applied exogenous Vc and 3 -carotene can protect effectively membrane system from osmotic stress, which displayed that the range of increase of membrane permeability and MDA content were lower that of control. The protective effect was significant especially in early stage of osmotic stress. While the protective function on chlorophyll was prominent in later stage and chlorophyll content was kept in higher level all along; Exogenous VE had a little effect on the avoidance of the increase of membrane permeability. On the other hand, it contribute to the reduction of MDA content and the protection of chlorophyll. Vc content of seabuckthron's leaf declined while Pro content increased evidently under osmotic stress were also tested .It is proved that these matters are the important factorin constitution of drought-resistance capability of seabuckthron.2.Epidermis feather play a very important role in drought-avoidance of seabuckthorn . there are many different types of epidermis feather .The epidermis feather of the stem includes astroid-hair, astroid peltate- hair, peltate- hair ; It of the leaf includes astroid-hair, astroid peltate- hair, peltate- hair and spiral-hair .we found that there are so much shock epidermis feather branching on surface of the stem and leaf ,and the similarity could be found too on nervation. There are not reported in stomata apertures of seabuckthorn ,however we found that the stomata apertures were distributed over the under leaf epidermis of sesbuckthorn.The guard cells were typical kidney-like.3.The mean relative water contents of 1m depth of soil were tested in different habitats. There are respectively data of 5 kinds habitats including shade (8.64%), semi-shady (7.50%), hill-top (7.12%), semi-sunny (6.41%), sunny (6.17%).The shade and semi-shady and other habitats had significant discrepancy. The shade also had a highest relative humidity 40.89%,however the sunny was lowest 28.98%.There were extremely significant discrepancy between the shady and the sunny and semi-sunny (o=0.01) .4.The outdoors-experiment results showed that the values of Tr of five kinds of habitats are different, Tr of semi-shade was relatively stronger (SJSug.cm^.s'^in the morning and others were weaker .With the variation of directions of sunshine ,the Tr of shady and sunny were declining meanwhile hill-top was steady.The semi-shady reach the peak(6.16ug.cm~2.s~' )of its Tr in 12:OO.In the afternoon ,these values of Tr all reduced in different extent except seabuckthorn of shady .especially semi-shady.The mean of the all day Tr of 5 habitats was ordered in semi-shade 4.18(ag.cm"2.s"1>shade3.29^g.cm"2.s"1>semi-sunny3.22|ig.cm"2.s"1>hill-t...
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