Studies On The Biological Process Mechanism Of Jerusalem Artichoke Remediating Saline-alkali Soil

Soil salinization has always been an important factor affecting the development of tidal flat planting and forestry in my country.The tidal flat area of Jiangsu is7.67×10⁵hm²,accounting for about one-seventh of the total area of the country.The development and utilization of tidal flats is of great significance to Jiangsu and even China.As a kind of energy crop,Jerusalem artichoke is resistant to salt and alkali,and it has strong viability and high economic value.The development and utilization of Jerusalem artichoke resources has important strategic significance for improving saline land and increasing reserve arable land resources in my country.Therefore,using natural Suaeda phytoe vegetation as a control,the relationship between plant-soil-microbes mediated by root exudates after planting Jerusalem artichoke was studied and to reveal the biological process mechanism of Jerusalem artichoke remediating saline-alkali soil.The main findings are as follows:1.The rhizosphere soil of Jerusalem artichoke contains fructose,glucose,sucrose and oligofructose（sucrose triose,sucrose tetraose and sucrose pentaose）.The contents of fructose,glucose and sucrose were 2.3×10^-3g·kg^-1,4.2×10^-3g·kg^-1,2.7×10^-3g·kg^-1,respectively,which were significantly higher than those of Suaeda salsa rhizosphere soil（P<0.05）,which are respectively 9.28 times,1.52 times,and 2.43 times that of Suaeda salsa soil.There is also a significant difference in the content of fructose in the rhizosphere and non-rhizosphere of Jerusalem artichoke（P<0.05）.The content in the rhizosphere soil is about 12.02 times that of the non-rhizosphere.Fructooligosaccharides were not detected in Suaeda salsa soil.There are many types of Jerusalem artichoke root exudates.In addition to sugars,they also contain some small molecules and volatile compounds.There are 32 species in the rhizosphere soil of Jerusalem artichoke,including alcohols（6 species）,phenols（1 species）,aldehydes（3 species）,ketones（2 species）,acids（2 species）,hydrocarbons（11 species）,amides（2 species）),esters（5 species）,there are 8 species in Suaeda rhizosphere soil,including alcohols（1 species）,phenols（1 species）,acids（1 species）,hydrocarbons（3species）,and esters（2 species）.In addition,there are unique components in the root exudates of Jerusalem artichoke,such as alkenals,alkanes,esters and some acids.Organic acids（n-hexadecanoic acid and octadecanoic acid）are released into the soil,reducing the p H of the soil and increasing the availability of soil nutrients.2.The root exudates of Jerusalem artichoke have many types and high content.The sugars in the secretions provide rich nutrients for soil microorganisms,allowing them to multiply.The total number of microorganisms in Jerusalem artichoke soil is significantly higher than that of Suaeda（P<0.05）.Among them,bacteria It also has a quantitative advantage.Soil microbial biomass carbon and nitrogen were higher than Suaeda salsa soil,and their values were 1.95 times and 1.6 times that of Suaeda salsa soil,respectively.Through the analysis of different diversity indexes,it was found that the coverage and uniformity of the soil microbial community of Jerusalem artichoke was significantly higher than that of Suaeda（P<0.05）,and there was no significant difference in microbial diversity between rhizosphere and non-rhizosphere soil.The dominant populations in Jerusalem artichoke soil,such as Proteobacteria,Actinobacteria,Chloroflexi,Acidobacteria,account for up to 90%,which is larger than Suaeda.Among them,the relative abundance of Actinobacteria and Acidobacteria was significantly higher than that of Suaeda（P<0.05）,and the difference of Proteobacteria between Jerusalem artichoke and Suaeda was not significant.Among the dominant populations,Actinobacteria and Acidobacteria were significantly positively correlated with invertase,urease,alkaline phosphatase,total phosphorus and alkaline hydrolyzed nitrogen（P<0.05）,and were correlated with salinity and available potassium Negative correlation（P<0.05）;Proteobacteria are mainly positively correlated with salt,available potassium and total potassium（P<0.05）,and organic matter,total phosphorus and total nitrogen are negatively correlated with them（P<0.05）;The difference between Chloroflexi and environmental factors is not significant.There are some peculiar phyla in Jerusalem artichoke soil,such as Nitrospinae,Halanaerobiaeota,Tenericutes,Dadabacteria,Spirochaetes.The increase in the number of beneficial microorganisms in the soil can produce more enzymes to be released into the soil,and significantly increase the activities of urease,invertase and alkaline phosphatase in the rhizosphere of Jerusalem artichoke（except catalase）（P<0.05）.They are 1.83 times,1.88 times and 3.30 times that of Suaeda salsa soil respectively.3.Single factor experiment and orthogonal experiment determined the best extraction process for inulin from fresh Jerusalem artichoke tubers:extraction temperature was 90℃,extraction time was 60 min,The material-to-water ratio is1:18,and the extraction is performed twice.The order of the primary and secondary effects of each factor is extraction temperature>extraction time>material-to-water ratio.The crude extract is purified and refined to obtain inulin products.1000g of fresh Jerusalem artichoke tubers can get 110g of inulin.By comparing the color and purity with commercially available inulin,it is found that the color of homemade inulin is slightly better than that of commercially available inulin.White,the content of total sugar,reducing sugar and inulin is slightly higher than that of commercially available inulin.The obtained inulin replaced the carbon source in the culture medium,and the activity of the screened functional bacteria was measured.As a result,it was found that using inulin as the carbon source promoted the growth and proliferation of functional bacteria.The bacterial suspension of the functional strains and the carrier are mixed in proportion to prepare a solid microbial inoculum,which is applied to a pot experiment.After the application of microbial inoculants,the plant height,root length,stem thickness,fresh weight,etc.of the plant were significantly increased,which significantly promoted the growth of the plant.It can be seen that after planting Jerusalem artichoke in saline-alkali land,under the mediation of root exudates,the number of soil microorganisms increased significantly（P<0.05）,the biological activity increased significantly,the relative abundance of soil beneficial bacteria groups increased significantly（P<0.05）,and the soil microbial community structure has been optimized.The activity of soil microorganisms promoted a significant increase in soil enzyme activity（P<0.05）,and the increase in enzyme activity accelerated the decomposition and mineralization of organic compounds in the soil,improved the properties of saline soil,and achieved the purpose of restoring saline-alkali land.