Study On Salt-alkali Tolerance Of Purple Root Eichhornia Crassipes And Improvement Of Saline-alkali Soil By Green Manure

In China,there are vast salinized lands and waters.The area where the precipitation is insufficient,the groundwater level is not high,the evaporation is strong,and the underground salinity is rising,which causes the soil and water environment in the area to show varying degrees of salinity.Into.Purple root Eichhornia crassipes has strong characteristics of purifying water,and has strong reproduction ability,wide distribution,low economic value,and certain nutritional value.It can be cultivated annually in the north or protected for wintering.Its research focuses on absorbing heavy metals.In terms of resource utilization,there is less research on salt and alkali tolerance and green manure application.In this paper,purple root Eichhornia crassipes is used as the research material.By measuring the morphological and physiological and biochemical indexes of purple root Eichhornia crassipes plants under different NaHCO3 aqueous solution concentration and NaCl aqueous solution stress,the principal component analysis is performed by using a single index of salt and alkali tolerance(?)and membership function calculation,and then comprehensively evaluate the response of purple root Eichhornia crassipes to different saline-alkali water treatment.At the same time,using medium saline-alkali soil as a material,purple root Eichhornia crassipes was made into green manure,and it was investigated whether it has improvement and effect on saline-alkali soil.By measuring various properties of saline-alkali soil under different concentrations of purple root Eichhornia crassipes green manure,using a single index to improve the saline-alkali soil coefficient(a)for principal component analysis and membership function calculation,and then comprehensively evaluating the moderate saline-alkali soil for different concentrations of purple root Eichhornia crassipes Green manure response.It is expected to provide a theoretical basis for its rich water plant landscape,improvement of the water environment and its resource utilization.The results show:(1)The pH value of the aqueous solution of purple root Eichhornia crassipes at 20 mmol·L-1 NaHCO3 was the most gentle;in low concentration NaHCO3 solution(?40 mmol·L-1),compared with CK,the morphological index showed an increase or no significant effect;in high-concentration NaHCO3 solution(?60 mmol·L-1),the morphological index of purple root Eichhornia crassipes decreased significantly;and when the stress level exceeded the threshold of purple root Eichhornia crassipes self-regulation,measured the obtained osmolyte content,enzyme activity and chlorophyll showed a continuous downward trend;NaHCO3 stress significantly affected the photosynthetic parameters of purple root Eichhornia crassipes.With the increase of NaHCO3 concentration and the extension of the test treatment time,Pn of purple root Eichhornia crassipes continued the downward trend is that Ci,Tr,and Gs are generally on the rise,and their photosynthesis is mainly restricted by non-stomatal.Comprehensive analysis shows that purple root Eichhornia crassipes has certain NaHCO3 tolerance,can normally survive in water bodies with a concentration of no more than 40 mmol·L-1 NaHCO3,and can improve the pH of water bodies with low NaHCO3 concentrations.(2)The pH value of the water solution of purple root Eichhornia crassipes decreased under the stress of low concentration NaCl(?50 mmol·L-1);the pH value of the water solution of purple root Eichhornia crassipes increased under the stress of high concentration NaCl(?75 mmol·L-1).In low-concentration NaCl solution(?50 mmol·L-1),compared with CK,the morphological index of purple root Eichhornia crassipes significantly increased,which promoted the growth of purple root Eichhornia crassipes;in high-concentration NaCl solution(?75 mmol·L-1),the morphological index of purple root Eichhornia crassipes showed no significant increase or decrease.With the deepening of NaCl stress,the measured maximum values of osmolyte content,enzyme activity and chlorophyll of purple root Eichhornia crassipes gradually shifted towards low-concentration NaCl.In low-concentration NaCl solution(?50 mmol·L-1),compared with CK,Pn and Gs of purple root Eichhornia crassipes first rise and then decrease.In high-concentration NaCl solution(?75 mmol·L-1),the Pn of purple root Eichhornia crassipes continued to decrease;the Ci of purple root Eichhornia crassipes was less than CK at the time of initial stress,and it rose overall with the duration of stress;Tr showed an overall upward trend.Comprehensive analysis shows that when initially stressed by NaCl,purple root Eichhornia crassipes is mainly limited by photosynthetic stomata.As the cumulative adversity reaches a certain level(too high concentration or long duration),purple root Eichhornia crassipes is mainly affected by photosynthetic non-stomata limit.Low concentration of NaCl(?50 mmol·L-1)can promote the growth and metabolism of purple root Eichhornia crassipes,and purple root Eichhornia crassipes can survive in water with a concentration of not more than 75 mmol L-1 NaCl.(3)Purple root Eichhornia crassipes green manure has certain feasibility to improve moderate saline-alkali soil.Different concentrations of purple root Eichhornia crassipes green manure can significantly reduce soil bulk density and soil total salt of medium saline-alkali soil in a short time(35 d).Content and pH value,and can significantly increase the soil water content,soil porosity and soil microorganisms in moderate saline-alkali soil.Comprehensive analysis shows that purple root Eichhornia crassipes green manure can effectively improve the microbial activity of moderate saline-alkali soil,increase the content and availability of nutrients in the soil,and the formation of soil fertility,which is helpful to the cultivation and cultivation of saline-alkali soil plants.