|Other Abstract||In the southern fringe of Taklamakan desert, with raging sandstorm, high temperature and drought, salinity serious, so it is a region of harsh environmental conditions area. And because of the human unreasonably use and destruction, it brings oasis periphery of serious damage to the natural vegetation, which results in soil salinization problems have become increasingly prominent. Alhagi sparsifolia Shap. is one of the dominant plant species in the southern edge of the Taklimakan Desert. With strong adaptability and widely distributed, it has a very important ecological benefits in sand-fixing, inhibiting grassland degradation and improving the surrounding environment. Therefore, it is necessary to reveal the adaptation rules for salt of A. sparsifolia, and it is also urgent to accelerate the peripheral oasis vegetation restoration. The study relies on the ecology experimental research platform of Cele Desert Research Station which is located in the southern edge of the Tarim Basin. And it expands the control experiment that is the effect of different concentrations of salt on A. sparsifolia at different growth stages. It also researches the seedlings growth, morphological characteristics, biomass allocation and root growth characteristics as well as the growth of ramets of A. sparsifolia under continuous salt conditions. To further reveal the A. sparsifolia seedlings settlement process and update rule under the condition of salinity, and provide the basis for artificial A. sparsifolia vegetation restoration in the region. Our main results were identified as follows:
(1) The aspect of seed emergence: As the salt concentration increases, the A. sparsifolia seed germination rate, seedling index first increases and then decreases. It also reaches the maximum at 200 mmol/L salt condition, and different salt conditions delays A. sparsifolia seed emergence. Further indicates A. sparsifolia seed emergence salt suitably ranges from 0~200 mmol/L.
(2) The aspect of seedlings growth: ① The A. sparsifolia height and width decreases with increasing salt concentration, total biomass in the treatment for 30 days is no difference in low concentration (<200 mmol/L), in the treatment for 65 days obviously decreases in high concentration (400 mmol/L). The A. sparsifolia net photosynthetic rate decreases with increasing salinity concentration, water use efficiency significantly increases in the concentration of 400 mmol/L. In the treatment for 30 days its chlorophyll a, b and total chlorophyll content reduces in the 400 mmol/L concentration, and it is no significant difference between the low concentration (<200 mmol/L) conditions. Comparing with 30 days treatment, the A. sparsifolia for 65 days treatment its chlorophyll a, b, total chlorophyll content and carotenoid content are lower, and they are all gradually decreases with increasing salt concentration. The A. sparsifolia seedlings that deal with 30 days specific leaf area and leaf dry matter content decreases with increasing salt concentration. When dealing with 65 days, its specific leaf area increases with increasing salt concentration, but leaf dry matter content obviously decreases. The A. sparsifolia seedlings nitrogen content is no significant difference in low concentration (<200 mmol/L), but decreases in the concentration of 400 mmol/L, and phosphorus content first reduces and then increases with increasing salt concentration. It shows that high concentration of salt conditions affects not only the accumulation of biomass but also photosynthetic, pigment content, nitrogen and phosphorus content of A. sparsifolia seedlings. ② The A. sparsifolia root biomass that deal with 30 days in low concentration (<200 mmol/L) less than control, high concentration condition significantly reduces, and its root-shoot ratio is no significant difference between different salt conditions. The A. sparsifolia root biomass that deal with 65 days first increases and then decreases with increasing of salt concentration, and its root-shoot ratio also shows similar discipline. It indicates that is an effective strategy to adaptation to salt environment of A. sparsifolia through increasing the root-shoot ratio, its root biomass and root-shoot ratio significantly decreases under high concentration also reflects A. sparsifolia growth is inhibited.
(3) The aspect of biomass allocation: The A. sparsifolia proportion of stem and root weight that dealing with 30 days in high concentration (400 mmol/L) less than control, with increasing of salt concentration its leaf proportion gradually increases. The A. sparsifolia stem proportion that dealing with 65 days is no difference between (<200 mmol/L) salt conditions, high concentration condition significantly increases, its leaf proportion first decreases and then increases with increasing of salt concentration, root proportion increases under low concentration (<200 mmol/L), and decreases in high concentration. The A. sparsifolia that dealing with 65 days compares with dealing with 30 days stem and leaf weight proportion decreases, but root weight proportion increases. It shows that the A. sparsifolia in salt treatment early (for 30 days) allocates more biomass to shoot resources to compete for light, and in the 65 days after treatment, it allocates more biomass to root to adapt to salt environment.
(4) The aspect of ion distribution: At different concentrations of salt conditions, Na+ contents distribution in different organs of A. sparsifolia seedlings substantially: stem> leaf > root. And K+ in different organs of A. sparsifolia seedlings substantially: stem and leaf > root. With increasing salt concentration, its K+/Na+ in roots first increase and then decrease, in stems decrease all the time, in leaves the overall decreasing trend. The phenomenon illustrates that either low salt concentrations or high salt conditions inhibits the absorption of K+ in different organs of A. sparsifolia seedlings, and aerial parts (stems and leaves) inhibition greater than belowground (root).
(5) The aspect of ramets formation: The A. sparsifolia is clone plant, and it competes light, water and nutrient resources to adapt to the evil environment by producing ramets. Under good moisture conditions, annual A. sparsifolia can produce more ramets for good asexual reproduction. In the present study, only the control condition (50 mmol/L) to form ramets, which indicates that the low concentration salt conditions (0~50 mmol/L ) is in favor of the formation of A. sparsifolia ramets.|