Effects Of Exogenous Nitrogen On Rhizosphere Microbial Community Structure And Accumulation Of Medicinal Components In Phellodendron Chinense Schneid

Phellodendron chinense Schneid.is a typical medicinal economic plant in the south of China,It contains alkaloids,flavonoids,sterols and other medicinal components,so it is widely used in clinical treatment and research.With the development of society and the gradual improvement of people’s living standards,traditional Chinese medicine treatment and self-cultivation have been accepted and recognized,resulting in an increasing demand for Phellodendron chinense Schneid.Therefore,it is a convenient way to improve the yield and quality of Chinese herbal medicines such as Phellodendron chinense Schneid.by adjusting the cultivation measures reasonably.Reasonable application of nitrogen fertilizer can increase plant yield,improve crop quality,and can also effectively promote root growth,improve soil nutrient status,and increase soil enzyme activity.Therefore,in this study,annual Phellodendron chinense Schneid.seedlings were used as experimental materials,and field experiments were used to systematically study the effects of CK(control),N5(5 gN/m2),N10(10 gN/m2)and N15(15 gN/m2)on root growth,soil physical and chemical properties,soil enzyme activity,nitrogen metabolism-related gene expression levels and the effects of changes in microbial diversity,to clarify the effects of exogenous nitrogen on root growth and content of medicinal components of Phellodendron chinense Schneid.,and to clarify the mechanism of the interaction between nitrogen and soil microorganisms.Fertilization and scientific planting provide theoretical basis.The main results are as follows:1.After applying different concentrations of nitrogen fertilizer,the pH value in the rhizosphere soil of Phellodendron chinense Schneid.seedlings decreased significantly,reduced total phosphorus content,the organic matter content showed N10<CK<N15<N5,but the soil total nitrogen content had no significant change;The contents of nitrogen,nitrate nitrogen,available phosphorus and available potassium increased,and the contents of ammonium nitrogen,nitrate nitrogen and available phosphorus were the highest in N10 treatment.2.Compared with CK,N5,N10 and N15 increased the activity of catalase in soil and significantly decreased the activity of soil urease;the increased activity of soil acid phosphatase under N10 treatment was the highest;N5 and N10 increased the activity of soil sucrose enzyme activity,while N15 reduced soil sucrase activity.3.Compared with the CK group,the N5,N10 and N15 treatment groups significantly decreased the Chao 1 and shannon indices of soil bacteria;the N5 and N10 treatment groups had higher ACE and Chaol indices of soil fungi than the CK group,and the N10 and N15 treatment groups increased the Shnnon index.The main bacterial phyla included:Proteobacteria,Acidobacteria and Bacteroidetes,the main fungal phyla included:Basidiomycota,Ascomycota,Chytridiomycota;Correlation heat map analysis showed that Nitrospirae had a very significant negative correlation with NH4+N,NO3--N,AP,and a very significant positive correlation with pH,Acidobacteria and Basidiomycota was significantly positively correlated with SOM.Actinobacteria and Chytridiomycota were positively correlated with NH4+-N.At the same time,through RDA analysis,it can be seen that pH,SOM,NH4+-N,NH3--N and AP are also the main environmental factors affecting rhizosphere microorganisms.4.Exogenous nitrogen increased the relative expression abundance of amoA,nirK and phoD genes,and there was no significant difference in the relative expression abundance of nifH gene among the treatments.5.Exogenous nitrogen increased the relative expression of Pc(S)-AMT1 gene in the roots of Phellodendron chinense Schneid.seedlings,promoted the accumulation of ammonium nitrogen and nitrate nitrogen,and the promotion effect was the best under N10 treatment;Simultaneously increased the enzymatic activities of GS and NR in roots,as well as the expression levels of Pc(S)-GS(N5 and N10 levels)and Pc(S)-NR(N10 and N15 levels);Exogenous nitrogen significantly increased the total root length,root diameter,root surface area,root volume and root fresh weight of Phellodendron chinense Schneid.seedlings,and N10 had the best promoting effect.6.Exogenous nitrogen significantly increased the expression level of Pc(S)-THBO gene in the roots of Phellodendron chinense Schneid.seedlings,and also significantly increased the contents of phellodendron and berberine in roots,and N10 had the best promotion effect.The results of correlation analysis showed that Phellodendron chinensis and berberine in the roots of Phellodendron chinense Schneid.seedlings were closely related to soil ammonium nitrogen、nitrate nitrogen、available phosphorus,acid phosphatase、soil fungal ACE index、total root length、root mean diameter、root surface area、root volume、root diameter、root fresh weight、root ammonium nitrogen、root nitrate and nitrate reductase.Combining the root growth indicators of Phellodendron chinense Schneid.seedlings and the results of soil microenvironment,N10 was the optimum exogenous nitrogen concentration to promote the growth of Phellodendron chinense Schneid.seedlings,and established the relationship between exogenous nitrogen—soil available nutrient content-soil fungal diversity—root growth and small size of Phellodendron chinensis.The regulation model of berberine synthesis provides theoretical basis and data support for the follow-up in-depth study of exogenous nitrogen promoting root growth and berberine accumulation of Phellodendron chinense Schneid.seedlings and scientific cultivation.