Abstract: [Objective] Desertification is one of the important ecological and environmental problem in Xinjiang, and habitat drought is a major limiting factor for vegetation growth in this region. Thus, understanding physiological and ecological adaptability and drought tolerant of sandy shrub is of great significance for selective breeding and vegetation restoration in desert area.[Method] Five sandy shrubs, i.e. Caragana korshinskii, Morus alba var. multicaulis×M. mongolica, Atraphaxis bracteata, Calligonum rubicundunm, Salix psammophila, were subjected to four water gradients of T1 (CK, 12 000 m³·hm^-2), T2 (9 600 m³·hm^-2), T3 (7 200 m³·hm^-2), and T4 (4800 m³·hm^-2) in growth season. The duration of water treatment were divided into three stages of early stage (July), medium stage (August) and late stage (September). The ecophysiological indexes of net photosynthetic rate (P_n), transpiration rate (Tr), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), water potential, chlorophyll, the proline (Pro) content, soluble sugar content, superoxide dismutase (SOD) activity, peroxidase (POD) activity and soluble protein content were measured.[Result]1) The photosynthetic indexes and water potential of sandy shrubs decreased with the stress intensifying, except for chlorophyll contents of C. korshinskii at medium stage and S. psammophila at late stage of treatments. 2) The P_n of five shrubs gradually decreased and C_i was increased with stress intensifying. The Tr and G_s of A. bracteata, M. alba and S. psammophila increased from early to medium stage of treatment, and significantly decreased at late stage. The water potential of all shrubs at early treatment stage was from -0.93 to -2.34 MPa, and further reduced by 14.38 MPa and 12.22 MPa at the medium and late stage. The chlorophyll content of C. rubicundum was significantly lower than others. The SPAD of S. psammophila in medium and late stage was 47% of that at early stage. 3) At the late treatment stage, the activities of SOD and POD of each species varied greatly, and the maximum values were 10 times and 323 times higher than that of the minimum value, respectively. The Pro, soluble sugar and soluble protein content, SOD and POD activity of five shrubs increased gradually under mild drought stress, and they began to gradually decline with the stress intensifying. The MDA of M. alba var. multicaulis×M. mongolica decreased gradually but that of other shrubs increased with the increase of drought degree, especially for C. rubicundum, its MDA content under severe stress was 3.47 times higher than that of CK (T1). 4) The Pro content, soluble sugar content, and C_i of shrubs showed a very strong correlation with the first principal component. The score order of principal component was A. bracteata > C. korshinskii > M. alba var. multicaulis×M. mongolica > C. rubicundum > S. psammophila. All species had the negative factors score under severe drought stress (T4).[Conclusion] Under drought stress, each species improved their adaptability through accumulating more osmotic adjustment substances and improving antioxidant enzyme activity, but severe stress reduced their photosynthesis, transpiration and other physiological activities. A. bracteata, C. korshinskii, and M. alba var. multicaulis×M. mongolica have better drought resistance than C. rubicundum and S. psammophila. The content of Pro, soluble sugar content and C_i can well indicate the drought resistance ability of the five sandy shrubs.

Key words: sandy shrub, drought stress, drought resistance, physiological index, comprehensive evaluation