The Characteristics Of Bruguiera Gymnorrhiza Root Exudates And The Relationship Between Root Exudates And Degradation Of PAHs In Rhizosphere

Polycyclic aromatic hydrocarbons(PAHs),hydrophobic biodegradable persistent organic compound,which is widely distributed in the environment and has a strong role in the carcinogenic and teratogenic effects and mutagenic "three letter" role。How to improve the bioavailability of PAHs has been the focus of our attention all the time.It had been reported that root exudates components and microbial had great importance on organic pollutants remediation.The low molecular weight organic acids and soluble sugar were the main component of root exudates.Bruguiera gymnorrhiza,a sort of Mangrove,was used as the test material in my paper to study stress response of the root exudates under different concentrations of three typical PAHs(phenantlrene,pyrene and benzo[a]pyrene)by three indoor culture experiments including the "water culture coercion","simulated root exudates add" and "pot experiment",which can further explore the PAHs in plants-intrinsic mechanism under the combined effects of the removal of microorganisms It will provide a theoretical basis for the research on plant rhizosphere effect and PAHs Remediation in different environmental media subsequently in-depth.The main conclusions are as follows:(1)There was a big difference in the GC-MS component of Bruguiera gymnorrhiza root exudates between hydroponic rhizosphere.rhizosphere sediments and non-rhizosphere sediments in which there were 9 spieces of compounds are in common.It was mainly hydrocarbons under hydroponic conditions,sediment types with phenols and esters based.The concentration of soluble organic carbon(DOC),total soluble sugars(TS)in rhizosphere and non-rhizosphere sediments were higher than the corresponding concentrations of both in hydroponic conditions,while at the same time root exudates hydroponic organic low molecular weight organics acid-based,and tartaric acid as the dominant;Low molecular weight organic matter in sediments places sugar-based,and tartaric acid was still the main acid in low molecular weight organic acids,concentration:rhizosphere>non-rhizosphere.(2)The response of Bruguiera gymnorrhiza root exudates under-PAHs pollution stress:Under hydroponic condition,the proportion of hydrocarbons decreased after the stress,with lactam compounds increased.The amounts of dissolved organic carbon(DOC),total soluble sugars(TS)and total organic acids(TOA)increased first and decreased thereafter with the increase in the number of days,finally reached the maximum on the fiftheenth day.Through pot experiment,the compound species in rhizosphere soil sediments increased after stress of phenanthrene and pyrene and the proportion of aldehydes increased,with esters accounting decreased,when DOC concentration reduced,TOA concentration increased with the elevated stress concentrations,while the classes of compounds reduced after-benzo[a]pyrene stress,the changement of DOC and TOA concentration under stress of phenanthrene and pyrene was in contrast.DOC concentrations decreased slightly in Non-rhizosphere sediments,but still larger than the rhizosphere sediments,while TOA concentrations was lower than the rhizosphere sediments;Overall,in different media,macromolecular compound types in root exudates varied after PAHs Stress,and no significant changes in the composition of small molecule compounds,which will vary with changes in stress concentration on the concentration.(3)Compared with the control,PAHs degradation rate was higher than the treatment group with plants or added artificial root exudates.From the research results,in the presence of microorganisms,the ability of PAHs degradation in various root exudates components from high to low was:AREs>organic acids>sugar.Three kinds of PAHs in the same concentration of the same kind of stress or add root exudates treatment,PAHs degradation rate from high in the end was as follows:phenanthrene>pyrene>benzo[a]pyrene.This indicated the presence of root exudates significantly strengthened PAHs degradation,and low molecular weight PAHs was more easily degraded.