Study On The Drought Resistance Of 5 Shrub Species In Semi-arid Valley Of Lhasa River

Five native species in semi-arid valley of Lhasa River: Sophora moorcroftiana, Hippophae gyantsensis, Berberis hemsleyana,Caragana maximovicziana and Rosa sericea were selected for the experimental materials, drought-resistant physiological and biochemical index of them were studied under different content of soil water in pot in order to reveals the differences between the five species in physiological and biochemical responses and evaluate the drought resistance of them, which provide a theoretical basis for selecting afforestation tree species suitable for semi-arid regions in Tibet. The main conclusions are as follows:1. Under drought stress, the soil moisture of each species gradually decreased, various tree species suffered basically the consistent intensity of drought stress, and there is no significant difference(P>0.05), thus ensuring that the identity of the drought conditions and the reliable analysis of differences in various tree species.2. Leaf water content and relative water content of five species decreased with the decline of soil water content, which Rosa sericea the biggestdrop, followed by Caragana maximovicziana, Berberis hemsleyana, Hippophae gyantsensis and Sophora moorcroftiana.3. Chlorophyll content of five species also decreased. To the later stage of drought stress, chlorophyll of Rosa sericea decline 55.73% compared with the CK, followed by Caragana maximovicziana(36.54%), Berberis hemsleyana(32.96%), Hippophae gyantsensis(27.09%), and Sophora moorcroftiana is the minimum(19.17%).4. The proline content and soluble sugar content of five species showed an upward trend overall. On the 28th day of drought stress, Hippophae gyantsensis, Rosa sericea, Sophora moorcroftiana, Caragana maximovicziana and Berberis hemsleyana Pro content increased 3.5, 2.8, 1.1, 1.3 and 3.4 times; the soluble sugar content of five species increased slowly, but the soluble sugar content of each species have higher growth on the 28th day of drought stress compared with the CK. Berberis hemsleyana increased 210.86% compared with the CK, followed by Sophora moorcroftiana (125%), Hippophae gyantsensis(88.23%), Rosa sericea(77.92%) and Caragana maximovicziana (43.18%).5. The injury degree of five species'membrane system increased, reflected in the five species'increase of relative conductivity and malondialdehyde content. Compared with the CK of various species, the largest relative conductivity rate increase is Rosa sericea, followed by Caragana maximovicziana, Berberis hemsleyana and Hippophae gyantsensis, Sophora moorcroftiana has smallest increase in the relative conductivity. MDA content of Sophora moorcroftiana has the smallest increase, only 29.15% increase compared with the CK, then followed by Berberis hemsleyana, Hippophae gyantsensis, Caragana maximovicziana, the most intense peroxidation and the largest MDA content is Rosasericea.6. The overall trend of SOD, POD and CAT activity of five species emerged first, and then decreased. 1-7days of drought stress, the SOD, CAT, POD activity of each species was in an uptrend; the SOD, CAT, POD activity of Rosa sericea reached the climax on the 7th day of drought stress, then decreased; on the 14th days of drought stress, the SOD, CAT, POD activity of Hippophae gyantsensis, Caragana maximovicziana and Berberis hemsleyana began to decline; the SOD and POD activity of Sophora moorcroftiana reached the climax on the 21th day and then decreased, while its CAT activity maintained an upward trend all long.7. The main factor analysis method was used to analyze ten physiological and biochemical indexes of five species, the result showed that leaf water content, relative water content, superoxide dismutase, malondialdehyde content, soluble sugar content, peroxidase, chlorophyll content and relative electrical conductivity were the most important 8 indexes to evaluate the drought resistance of the each species.8. Through the method of subordinate(anti-subordinate)function, comprehensive assessment on the drought resistant index of five species indicated that the order of drought resistance capability of 5 shrubs was Sophora moorcroftiana > Hippophae gyantsensis > Berberis hemsleyana > Caragana maximovicziana> Rosa serrul.