Study On The Salt-Alkali Tolerance Threshold Of Fraxinus Mandshurica Saline-Alkali Proven Seedlings

Due to the rise in global temperature and irrational fertilization methods,salinized land has increased year by year,affecting plant growth.However,vegetation that has long grown in saline habitats has developed some saline tolerance.Correct assessment of vegetation reproductive potential in saline-alkali habitats is of great significance for the development of germplasm resources in stressful environments.In this study the annual Fraxinus mandschurica seedlings of saline-alkali seed sources were used as the research object,and the suitable seed sources were used as the control group,and 8 different concentrations of 0and 25 mmol·L^-1、50 mmol·L^-1、100 mmol·L^-1、150 mmol·L^-1、200 mmol·L^-1、250 mmol·L^-1、300 mmol·L^-1mixed soda saline（Na CO₃,Na HCO₃in 1:1）combination for potting testing.By observing the morphological changes and physiological responses of saline-based Fraxinus mandschurica and control seed sources in different concentrations of soda saline solution,the salinity tolerance and threshold of saline-alkali seed-source ash seedlings were analyzed.The main findings are as follows:1.The average survival rate of Fraxinus mandschurica from saline seed sources was 3%higher than that of the control at 1 and 8 concentrations,and the salinity index was 0.03 lower than that of the control.2.The average biomass of saline seed source Ash is 18%higher than that of the control,the average leaf area is 5%higher than the control,the average seedling growth is higher than the control 23%,and the average diameter growth is higher than the control 36%.The leaf thickness is 4%higher than that of the control.3.The average net photosynthetic rate of Fraxinus mandschurica from saline seed source was 24%higher than that of the control the chlorophyll content was higher than that of the control by 24%,and the leaf water content was higher than that of the control by 33%.4.The average soluble sugar content of saline-alkali seed sources was 38%higher than that of the control,the soluble protein was 42%higher,the sodium ion was 9%lower than that of the control,and the potassium ion was 5%higher than that of the control.Malondialdehyde（MDA）levels were 1%lower than the control,superoxide dismutase（SOD）was 10%higher than the control,peroxidase（POD）was 3%lower than the control,and catalase was 28%higher than the control.5.The average total C content of saline-alkali seed sources was 1%higher than that of the control;the total N content was lower than that of the control by 8%,and the total P content was 7%higher than that of the control;the CN ratio was 7%higher than that of the control;and the NP ratio was 5%higher than that of the control.In summary,the salinity tolerance of Fraxinus mandschurica seedlings from saline seed sources is greater than that of control seed sources.Establishing a regression equation with a biomass reduction of 50%defined as the tolerance threshold of the plant yielded saline-alkali seed seedlings was 170 mmol·L^-1,control seed source of 159 mmol·L^-1。...