Effects Of Microbial Community On Crop Growth And Phytohormones

Phytohormones are trace organic compounds synthesized by plants themselves and can be involved in regulating the growth and development of crops at very low concentrations.In addition to plants,microorganisms can also secrete phytohormones,so soil,especially in rhizosphere soil,contains phytohormones.However,the content of phytohormones in soil is extremely low and the soil matrix composition is complex,which makes it difficult to detect phytohormones in soil.Studies on phytohormones in soil are scare and mostly focus on few of the diverse phytohormones,while many phytohormones do not exist alone,but interact with each other to synergistically affect the growth of crops.In addition,most studies focus on the ability and function in vitro pure culture microorganisms to secrete phytohormones,and lack of in-depth studies on bulk soil,rhizosphere soil and root phytohormones interaction.So we conducted this research,firstly,to establish UPLC-MS/MS method for simultaneous determination of multiple phytohormones in soil and crops.Then we conducted the rice and maize pot experiment,using UPLC-MS/MS method and molecular biology technology,to study the variation of phytohormones in maize and rice roots,rhizosphere soil and bulk soil under different microbial environments,relationship between rhizosphere phytohormones and crop growth,and the correlation between phytohormones and microbial community structure.The main research results are as follows:1.UPLC-MS/MS was established for simultaneous determination of multiple phytohormones in soil and crops.The pretreatment of this method does not require overnight extraction.After adding dichloromethane,ultrasonic centrifugation and redissolution,the extracts can be directlymeasured,which greatly saves the time of sample pretreatment.The UPLC-MS/MS method is easy to operate,good selectivity,high sensitivity,and suitable for the simultaneous detection multiple phytohormones in soil and plants.2.The change of soil microbial community structure will affect the growth of maize and rice as well as the typies and concentration of rhizosphere phytohormones.3.The growth of maize and rice is correlated with phytohormones,for example,auxin,cytokinins,strigolactones,and the total of growth-promoting phytohormones are positively correlated with the growth of maize and rice,while abscisic acid,jasmonic acid,salicylic acid and the total of anti-defense phytohormones are negatively correlated with the growth of maize and rice.4.There is a certain correlation between phytohormones and microbial community,for example,auxin,cytokinins,strigolactones,and the total of growth-promoting phytohormones were significantly positively correlated with Actinobacteria,Chloroflexi,Planctomycetes,Thaumarchaeota,and negatively correlated with Firmicutes while abscisic acid,jasmonic acid,salicylic acid and the total of anti-defense phytohormones were significantly positively correlated with Actinobacteria and negatively correlated with Proteobacteria.This research reveals that the change of microbial community structure may affect the growth of maize and rice,and the mechanism of affecting the growth of crops may be that,the change of microbial community structure may affect the species and concentration of rhizosphere phytohormones which in turn affect crop growth.Due to the complex diversity of the rhizosphere,crop growth is affected by multiple factors at the same time.Phytohormone are just one of the signaling substances among many factors.Our study only provides a theoretical reference for the study of soil-microbe-crop interaction.The effect of phytohormone on crop growth needs further research and verification.