Study On The Coupling Relationship Between Polyphenols And Soil Characteristics And Their Biological Activities In Poplar Forest In Songnen Plain

Poplar is the main afforestation tree species in Songnen Plain,which has important ecological and economic value.The secondary metabolites of plants play an important role in improving self-protection and environmental adaptation.These secondary metabolites,especially polyphenols in phenols,not only have important medicinal value,but also play an important role in plants’ resistance to natural enemies and stress.There are also studies showing that soil physical and chemical properties,environmental factors and plant polyphenols have a very important relationship.Therefore,based on the previous study,this study selected poplar in Songnen Plain as the research object,studied the physical and chemical properties of soil,the polyphenol content of poplar and their coupling relationship in six sites(Lanling,Zhaozhou,Zhaodong,Dumeng,Mingshui and Fuyu),and focused on their antioxidant and antibacterial activities.The main results are as follows:1.Single factor and response surface design experiments were used to determine the optimal extraction process of polyphenols from poplar leaves,branches and bark.The results showed that the content of polyphenols in poplar leaves and branches was different in different areas(P<0.05),but not in bark(P>0.05).The content of polyphenols in leaves,branches and bark of Populus was 40.78 mg/g,46.51 mg/g and 47.07 mg/g respectively.2.The physical and chemical properties(organic matter,nitrogen,phosphorus and potassium,alkali hydrolyzed nitrogen,available phosphorus and available potassium;specific gravity,bulk density,porosity,water content,pH and conductivity)of soil in six sites of Songnen Plain were measured in detail.The results of variance analysis showed that there was no significant difference in the indexes of soil potassium,conductivity and bulk density between different sites(P>0.05),and the indexes of remaining physical and chemical properties showed different degrees The regional difference was significant(P<0.05).The contents of organic matter,total nitrogen and available phosphorus in Mingshui area were significantly higher than those in other areas(P<0.05),and the pH value in Dumeng area was the highest among the six sites;the contents of alkali hydrolyzed nitrogen and total phosphorus in Lanling and Zhaozhou areas were the highest,respectively;the soil water content in affluent areas was significantly higher than that in other areas.3.Soil physical and chemical properties,environment and stand characteristics are important factors affecting plant polyphenol content.The correlation analysis of Pearson data in the study area showed that porosity,bulk density,water content,phosphorus and available phosphorus content had an impact on them,among which,phosphorus content and available phosphorus had the most significant correlation with polyphenols in leaves,branches and bark(P ＜0.01);environmental factors and plant polyphenols had no significant correlation(P＞ 0.05);only tree density had an impact on bark in the stand characteristics The content of polyphenols was significantly negative correlation(P ＜0.01);the RDA sequencing analysis further showed that the interpretation of phosphorus,porosity,bulk density,water content and alkali hydrolyzed nitrogen in single factor analysis was more than 10%,and reached statistical significance(P ＜0.05).The results showed that the polyphenols of poplar were mainly affected by phosphorus content(Interpretation degree reached 22.3%),followed by soil porosity.4.The antioxidant and antibacterial activities of poplar were analyzed by DPPH free radical scavenging experiment and agar diffusion method.The results showed that the polyphenol extracts from all parts of poplar showed good DPPH scavenging ability,among which the bark had the strongest antioxidant capacity,and IC50 was 0.198 mg/ml.The results showed that the polyphenol extracts from different parts of poplar showed broad-spectrum antibacterial effect on Gram-positive bacteria(Bacillus subtilis,Staphylococcus aureus)and Gram-negative bacteria(E.coli,Acinetobacter baumannii).The inhibition range for Gram-negative bacteria was(11.01-14.33 ± 0.2 mm)and for Gram-positive bacteria was(15.05-25.97± 0.3 mm).On this basis,MIC and MBC results showed that polyphenol extracts from different parts of poplar had better inhibitory effect on Gram-positive bacteria than Gram-negative bacteria.In conclusion,poplar has strong antioxidant and antibacterial activities.In conclusion,the results of the study analyzed the differences of plant polyphenol content,soil characteristics and the coupling relationship with environmental factors.The results showed that poplar had high content of polyphenols,and had strong antioxidant and antibacterial activities.At the same time,the physical and chemical properties of soil showed different degrees of regional differences.RDA sequencing analysis found that the main factor affecting the polyphenol content of poplar in Songnen Plain was soil phosphorus content,followed by soil porosity.This study can provide theoretical basis and data support for the management and rational utilization of poplar resources in Songnen Plain.