The Growth And Physiological Response Of Nitraria Tangutorum Under The Salt Stress And The Evaluation Of Salt Tolerance

With the environment’s continuous deterioration and the development of industry and irrigated agriculture, the area of saline-alkali land is constantly expanding. It is a reasonable way to enhance the efficiency of the saline-alkali land use to select and promote salt-tolerant plants suitable for local growth. Instead of engineering measures, the measures of improving soil by plant can not only overcome the disadvantages of high costs, but also have lasting effective improvement effect on the soil. Nitraria tangutorum branches much, grows fast, breeds easy and is a good ecological shrub tree species with windbreak and sand-fixation efficiency and strong salt-tolerance. It has a great significance on improving the saline-alkali land and maintaining the balance of ecological environment and stability. The study regards 2 years cutting seedlings of Nitraria tangutorum introduced in the northern area of Shanxi as the research object, referring to the salt composition in the saline-alkali land in northern and northwest area of Shanxi Province, setting the neutral salt, alkaline salt, mixing salt, single salt, four components of different salt concentration gradient (100,200,300,400,500 mmol·L-1) to carry out the artificial simulation experiment of Nitraria tangutorum salt-tolerant, analyzing the growth and physiological response of Nitraria tangutorum seedling under different salt stress and the evaluation of salt resistance. The research aims at providing basis for popularization and application of soil improvement and vegetation restoration of Nitraria tangutorum in dry sandstorm area of northern and northwest of Shanxi Province. The main results are summarized as follow:1.The growth percentage of Nitraria tangutorum’s seedlings reaches the maximum value under the single salt stress of 200 mmol·L-1. The root to shoot ratio of seedlings was the highest under the neutral salt stress of 300 mmol·L-1,1.24 times more than the control group. The total biomass of seedlings was the highest under alkaline salt stress of 200 mmol·L-1. The growth, root shoot ratio and biomass of seedlings are relatively high under the mixed salt alkaline stress of lower concentration. The alkaline salt stress of high concentration (> 300 mmol·L-1) inhibited the growth of Nitraria tangutorum’s seedlings obviously.2. The chlorophyll content of seedlings under neutral salt and single salt stress increased first and then decreased, maintaining higher chlorophyll content compared with the other two groups. The chlorophyll content of the seedlings reached the highest under the stress of 200 mmol·L-1.3.The rate of electrolyte leakage of seedlings was relatively high under the mixed salt and alkaline stress and increased with the increase of the concentration of stress. However, the MDA content of seedlings under neutral salt stress was relatively high, increasing first and then decreasing. The rate of electrolyte leakage of seedlings reached the highest under the alkaline salt stress of 100 mmol·L-1. The rate of electrolyte leakage and MDA content of seedlings were relatively low under single salt stress and increased less with the increase of the concentration of salt.4.The activity of SOD under single salt stress was first increased and then decreased with the increase of the concentration of salt, but it has been maintained at a high level of activity compared to the other three groups. However, the activity of POD was relatively low compared to the other three groups. The activity of CAT under the mixed salt and alkaline stress was first increased and then decreased, maintaining higher activity compared to the other three groups.5.The activity of root under neutral salt stress was relatively high and increased first and then decreased with the increase of the concentration of salt, maintaining higher root activity compared with the other three groups.6.The comprehensive evaluation showed that:Nitraria tangutorum’s seedlings have good tolerance and adaptability to the single salt stress of low concentration(<300 mmol·L-1). The neutral and alkaline salt of high concentration inhibited the growth and physiological metabolism of seedlings. Nitraria tangutorum’s seedlings got the most serious damage under the mixed salt and alkaline stress.