| Phellodendron chinense Schneid(P.chinense Schneid)is a woody plant which belong to the Phellodendron genus of the Rutaceae family.Its stem bark and root bark contain medicinal components such as berberine and phellodendron,which have important effects on clearing heat and detoxifying,dispelling fire and dampness,and relieving stomach pain.The growth and accumulation of medicinal components of P.chinense Schneid seedlings are influenced by nutrients such as nitrogen(N)and phosphorus(P),and then affect its yield and quality,but the mechanism of nitrogen and phosphorus addition regulating the root growth and soil microbial diversity of P.chinense Schneid seedlings is not clear.Therefore,using the seedlings of P.chinense Schneid as experimental materials in this study,and five experimental groups were designed:CK(0 gN/m2),N10(10 gN/m2),N10P5(10 gN+5 gP/m2),N10P10(10 gN+10 gP/m2),and N10P15(10 gN+15 gP/m2),the root growth,nitrogen distribution and medicinal component content in root under N and P addition were systematically studied to clarify the regulation of N and P addition during the processes of growth and alkaloid synthesis of this seedlings.the soil physicochemical properties,enzyme activity,gene expression level and differentially accumulated metabolites under N and P input were investigated for clarifying the regulatory effects of N and P addition on soil microenvironment,and then to reveal the mechanism of N and P addition promoting the root growth and alkaloid synthesis of P.chinense Schneid Seedlings.These results will provide a theoretical basis for scientific cultivation and quality improvement of P.chinense Schneid.The main findings of the study are as flowing:1.Compared with CK,N10P5,N10P 10 and N10P 15 significantly reduced the pH,SOM and TN content in the rhizosphere soil of P.chinense Schneid seedlings,while decreasing soil TP and AK content,but significantly increasing soil AP,NH4+-N and NO3--N content.Moreover,different concentrations of N and P additions decreased the activities of ACP,GC,UR and NAG in soil,and N10P5 and N10P10 increased activities of ACPT in soil,but N10P5 and N10P15 significantly increased the CAT activities in soil.2.Different concentrations of N and P additions significantly reduced the diversity of bacteria,and N10P5 and N10P15 treatments increased the diversity of fungi.The main dominant groups of bacteria were Proteobacteria,Acidobacteria and Verrucomicrobia,and the main dominant groups of fungi were Ascomycota,Basidiomycota and Mortierellomycota.The results of correlation and redundancy analysis showed that pH,SOM and TN were the main environmental factors affecting the microbial community composition in rhizosphere soil of P.chinense Schneid seedlings.3.N10P10 treatment significantly increased the relative expression abundance of glutamate dehydrogenase gene gdhA,succinyl coenzyme A transferase gene smtA and glyoxylate aminotransferase gene sga,whereas decreased the relative expression abundance of gene cex,endoglinase gene chiA,alkaline phosphatase gene phoD,alkaline phosphatase gene phoX and nitrite reductase gene nirS2.4.A total of 745 soil metabolites in the CK,N10 and N10P10 groups were identified,and 12 differentially accumulated metabolites(DAMs)were screened,namely Estriol,Adenosine,Hesperidin,Betaine,Arecoline,Carbendazim,Estrone Testosterone glucuronide,N-Acetyl-L-leucine,Oxymorphone,N,N-Dimethylaniline,and 2’-Deoxyadenosine,among with five DAMs(Estriol,Arecoline,Carbendazim,Estrone,and N-Acetyl-L-leucine)in N10P10 group were highest than that of CK group.Five bacterial phyla(Proteobacteria,Acidobacteria,Verrucomicrobia,Bacteroidetes and Nitrospirae)and four fungal phyla(Ascomycota,Basidiomycota,Mortierellomycota and Cercozoa)showed significant correlation with DAMs content,implying that the above microorganisms were involved in the synthesis and accumulation of DAMs in soil.5.Different concentrations of N and P additions significantly increased the root fresh weight,total root length and TP content,and increased TN content,berberine and phellodendrine contents in root of P.chinense Schneid seedlings,but N10P10 and N10P15 treatments decreased the soluble sugar content in the roots,indicating that N and P additions promoted root growth and alkaloid accumulation of P.chinense Schneid seedlings.This study showed that the different concentrations of N and P addition changed soil physicochemical properties and enzyme activities,and regulated the structure and diversity of soil microbial communities and the synthesis and accumulation of soil DAMs,improved the utilization efficiency of N and P for promoting root growth and the synthesis and accumulation of berberine of P.chinense Schneid seedlings.These results of this study provide a theoretical basis for the scientific cultivation and improvement of quality and efficiency of P.chinense Schneid. |
