| Using four native species (Acer stenolobum Rehd.var.megalophyllum.Sophora viciifolin,Quercus liaotungensis,Ostryopsis davidiana)of Loess Plateau as experiment materials and Pot culture experiments simulating different soil water status ,this paper mainly deals with water consumption characteristic and growth ,biomass allocation regular and WUE of different level of four native tree species under three different soil water. Time and space change of water metabolism, osmotic adjustment substance, principal protective enzyme activity, photosynthesis and photosynthetic pigment of four tree species of different soil water stress, we expected to discover difference of drought-resistance mechanism and comprehensive evaluateDrought-resistance characteristic of four native tree species are different. By experiment, we discovered ecological responses and adaptability mechanism with soil water stress. This result provided scientific basis of rational chosen tree species and plant construction in Loess Plateau. The mail results are as follows:1. Different soil water content had obvious affected on water consumption of 4 tree species. Time and date of the highest water consumption had notably difference. The highest water consumption of four tree species concentrated on 6,7,8 month. Soil water content decided on water consumption ,the trend is normal water>media stress> severe stress. According to sort with water consumption under different soil water content ,the trend is Sophora viciifolin > Ouercus liaotungensis > Acer stenolobum Rehd.var.megalophyllum>Ostryopsis davidiana . Sophora viciifolin has higher water consumption and WUE characteristic, Ostryopsis davidiana belong to low water consumption and WUE species and has the highest water coefficient. Acer stenolobum Rehdvar.megalophyllum was sensible to soil water deficit, but it grows under widely water condition and fine adaptability and higher survival rate. Quercus liaotungensis has low water consumption and high WUE characteristic and its seedling has weakly resistance on high temperature and strong light.2. Change regular of date transpiration rate of different tree species have obvious different under different month and climate. Transpiration rate of seedling on sun day surpass that of cloudy day and summers surpass autumns. Curve of transpiration rate of different seedling was single or two peaks. Transpiration rate declined with the deepening of soil water stress. Correlation analysis with transpiration and environment elements showed that sunlight has the stronger effect on transpiration rate secondly is air temperature and RH. Different responses to principle environment factor of different tree species under different soil water content.3. Different soil water content has affected water metabolism of 4 trees species. Acer stenolobum Rehdvar.megalophyllum has higher leaf water potential, keeping higher leaf water content. It has drought avoidance characteristic. Ostryopsis davidiana decreased leaf water potential to increase organ water content and has weakly leaf water retention capability. Change of leaf water potential and water content of Ouercus liaotungensis isstable. Sum up, Quercus liaotungensis and Sophora viciifolin has stronger drought-resistance characteristic.4. Different soil water content had obvious affected on osmotic adjustment substance and photosynthetic pigment content of four tree species. Leaf Soluble sugar content of four seedlings ascended with descending soil water content. Chant of leaf praline content has no obvious regular with growing and water deficit. Change of leaf K+ content has notable different with different growth stage and water deficit. Leaf K+ content of Sophora viciifolin has significantly surpassed other seedling; K+ content has positive correlation with drought-resistance. Change of leaf soluble protein content has complex with soil water decreasing. Chlorophyll content descended with prolonging water stress time, Chlorophyll a ascended and...
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