Study On The Characters Of Several Shrubs Under Water And Salt Stress Based On The System Of SPAC In Loess Plateau Region

Based on the ovservation of water movement in the system of Soil-Plant-Atmosphere Continuum, the paper studied the character of Zygophyllum xanthoxylon, Berberis vernae Schneid, Lycium potaninii Pojark, Shepherdia argentea on drought and salt stress in high and cold area of loess plateau, Qinghai province. Main problem that the paper have studied as follows: changing rules of soil moisture and atmosphere humidity, changing of water potential and transport of water in SPAC system under drought stress, changing rules of soil and plant water potential with the salt stress, transpiration changing of the plant with the stress of drought and salt, distinguishing the mechanism of plant for drought and salt sress.Main research results are as follows:1. Rainfall was not even in the growing season. It got to the least when the plants were in bloom, which lead to soil drought and restricted the growing of the plant.2. Daily changing of water potential of the plant had a single apex when the drought was not serious. As the drought got serious, daily changing of leaf water potential got two apexes. Daily changing breadth got bigger first and then smaller. Considering of daily changing breadth of leaf water potential and the relationship between it and soil moisture, the paper got the differences of these four shrubs in the ability to resist drought of the environment. The sequence was Lycium potaninii Pojark > Zygophyllum xanthoxylon > Shepherdia argentea > Berberis vernae Schneid. And as the experiment showed, leaf water potential had an close relationship with weather factors.3.With increasing of soil water stress, daily changing curve of transpiration of Zygophyllum xanthoxylum,Lycium potaninii Pojark changed from single peak to double peaks. However, that of Berberis vernae Schneid,Shepherdia argentea always had double peakes. Respectively, under the same horizontal gradient, transpiration of Zygophyllum xanthoxylum is the highest, while that of Shepherdia argentea is the lowest. This result showed that the former is higher transpiration plant,while the latter is lower transpiration plant.4.By measuring the water potential in different interfaces of the SPAC system, and calculat the resistance of water transferring. The results show that the resistance from leaf to atmosphere is much more than that from soil to leaf. By comparing SPAC water potential gradient of four plants, the water absorption capacity and the transpiration of Zygophyllum xanthoxylum is the strongest.5. The result of soil water content when plant withered is 6.67% of Zygophyllum xanthoxylon, 6% of Lycium potaninii Pojark, 6.08% of Berberis vernae Schneid, 6.79% of Shepherdia argentea. The efficiency of water using of potted plants are all above 85%. Based on the relatationship between leaf water potential and soil water content or based on the relatationship between leaf water potential and soil water potential is summed up four plants all belong to the plant that have low water potential to delaying dehydration.6.Under the same soil water content, leaf water potential was compared when the soil salt content is 0.5‰,15‰. Results showed that leaf water potential of all three testing plants were the highest,when the soil salt content was 5‰. In addition, the main meteorological factor which effect leaf water potential was changed. under the salt soil condition.7.Under the same soil water content, transpiration of testing plants are all the highest when the soil salt content is 5‰.In addition, main meteorological factors that effect transpiration of three testing plants are changed under different salt soil conditions.8. The efficiency of water of plants decreased as salt stress increased. By comparing, salt tolerance of plants is: Zygophyllum xanthoxylon > Shepherdia argentea > Berberis vernae Schneid.