| 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. Meanwhile, water shortages are one of the most serious problems in China’s agriculture and animal husbandry. Minqin County in Gansu is located in the temperate continental arid climate zone. Although drought has become the restriction of local agriculture and animal husbandry development in this region, some xerophytic shrubs show much stronger adaptability than other plants, which not only play a very good cover surface, fixing soil, reduce the evaporation of soil and increase organic matter, improve soil structure, soil improvement, but also has high feeding value and become an important vegetation in Minqin ecological restoration. 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 ecological environment and development of grassland animal husbandry.The main results are as below:1. With increased drought stress, RWC and water retention in lamina of4shrubs Caragana korshinskii, Nitraria tangutorum, Haloxylon ammodendron and Lespedeza bicolor decreased. And the descending order of RWC and water retention in vitro among these4shrubs after8h was:Caragana korshinskii>Nitraria tangutorum>Haloxylon ammodendron> Lespedeza bicolor.2. With the aggravation of drought stress, chlorophyll content of4shrubs increased first but then dropped. The decrease range of chla, chlb and chla/b value in Nitraria tangutorum is the smallest, followed Haloxylon ammodendron, and Caragana korshinskii is the biggest one. MDA content and relative conductivity in four shrubs increased with the increasing intensity of drought stress. Compared to the control, relative conductivity of cell membrane in Caragana Korshinskii and Lespedeza bicolor were higher as6.90and6.68times, respectively, indicating that the plasma membrane of these two shrubs suffered serious injury and led to a large number of ions inside extravasation. However, in the case of Nitraria tangutorumand Haloxylon ammodendron, it was only1.97and2.00times to that of controls, indicating that content of osmotic adjustment substances of Nitraria tangutorumand Haloxylon ammodendron was higher than Caragana Korshinskii and Lespedeza bicolor. Osmotic adjustment substances content of4shrubs putted up an rising tendency under low stress intensity. However, soluble protein content decreased with increasing stress intensity. And content of proline and soluble sugar also showed slowing trend of increase in different degrees during stress period.3. Under drought stress, activities of SOD, POD and CAT in four shrubs remained at a high level. And in the different treatment periods, three enzymes above showed different activities but showed some differences. With the increased intensity of drought stress, activities of SOD, POD and CAT continued to increase in Caragana korshinskii, while the other three species showed a trend of increase first but then decrease. The activities of SOD, POD and CAT in species with less drought resistance declined first accompanying stress time.4. At different levels of drought stress, four shrubs showed different drought resistance with presence of different drought index, which indicating the drought resistance diversity exhibited in each species. And different indicators identified different strengths and weaknesses shrubs withstand drought inconsistent, suggesting that they are in the event of drought stress, take a different adaptation mechanism. The results of drought resistance evaluation using fuzzy membership function in4shrubs were as below:Nitraria tangutorum> Haloxylon ammodendron> Caragana korshinskii>Lespedeza bicolor. |
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