Characteristics Of Cd Enrichment In Different Varieties Of Miscanthus And Analysis Of Bacterial Community In The Process

The issue of soil safety concerns the survival of all mankind because it not only influences the environment on which the mankind lives,but also directly determines the safety of crops.With the sharply accelerating industrial production worldwide in recent decades,up to 3×10⁴t of cadmium?Cd?is discharged into the global environment every year.Hard to naturally degrade and clear,Cd also features a high liquidity,about 87%of which will enter the soil,exerting a significant impact on soil composition and function,seriously reducing crop yields.If people directly or indirectly consume crops planted in contaminated soil,Cd will gradually accumulate in the human body,causing various health problems and serious death.Therefore,the treatment and remediation of soils contaminated with heavy metal have always been a focus of academic research.In the face of the increasingly serious soil environmental contamination problem,it is of more importance to treat and remedy the contaminated soil with appropriate remediation methods in a reasonable and effective manner.The phytoremediation technology is designed with excellent characteristics,such as ecological and environmental protection,significant effect,and low energy consumption,so it has become a hot spot in the research of remediation technologies.It was found in this study that the energy plant Miscanthus has strong ecological adaptability and can remedy the soil contaminated by Cd to some extent.At present,there are not many available studies on the remediation of soil contaminated with heavy metal Cd by Miscanthus,and there are fewer that integrated with microorganisms.The selection of Miscanthus variety and against Cd enrichment and the composition of rhizosphere bacterial community still need to be further explored.From the above,it is of great practical significance to carry out the study on selection of Cd-tolerant Miscanthus variety and composition of rhizosphere bacterial community.The potted cultivation was adopted in this study to probe into the growth,Cd enrichment and distribution of different varieties of Miscanthus under heavy metal Cd stress.To study the composition of the rhizosphere soil microbial community,16S rRNA-Illumina MiSeq NGS technology,integrated with PICRUSt function prediction,was introduced to analyze the composition and function of rhizosphere bacterial communities of different varieties of Miscanthus in the process of the Cd enrichment and contamination in soil.The study results are as follows:1.Under the treatment of Cd with a concentration of 50 mg·kg^-1,the Cd content in the tissues of different varieties of Miscanthus was root>leaf>stem from high to low;Potted experiments indicated that the abilities of Xiangza No.1,Wujie No.1,Nandi No.4,Xiangmang No.1,and Nandi No.3?Miscanthus varieties?presented significant differences in absorption,transportation and accumulation of Cd under the stress of 50 mg·kg^-11 Cd,but the rhizosphere and aboveground part had higher TI values?TI>70?,tolerant to high-concentration Cd.The Cd content and enrichment coefficient?BCF>1?in the root were much higher than those of aboveground part,and the transfer coefficient TF was low,indicating that Cd is mainly enriched in the roots and the ability to transfer from the roots to the aboveground part was weak,and Miscanthus has the ability of fixation and remediation.The plant height and biomass of Nandi No.4 had the smallest decrease compared with those of the control group,and the extractable Cd content with NH₄OAc in the rhizosphere soil had a large decrease,suggesting that the Nandi No.4 Miscanthus variety had the strongest ability to fix and remedy heavy metal Cd.2.In the rhizosphere soil samples of 5 Miscanthus varieties,a total of 37 divisions,95 classes,185 orders,339 families,and 613 genera of bacteria were detected.The composition and structure of bacterial community in the rhizosphere soil samples of different varieties of Miscanthus presented certain differences.In terms of richness and diversity,the rhizosphere soil of Miscanthus planting soil free of Cd contaminatio n was higher than that of 50 mg·kg^-11 Cd contaminated soil.The predominant bacteria in the rhizosphere soil samples of Miscanthus at the level of divison,class,order,famil,and genera were Proteobacteria,Acidobacteria,Bacteroidales,Bacteroidaceae,and Bacteroides.3.Cd addition may increase the richness of bacteria such as RB41 in Blascotella-ceae?Subgroup₄?,Flavisolibacter in Chitinophagaceae,Sphingomonas in Sphingomon-adaceae.These bacteria were provided with a higher tolerance to Cd.The proportion of the Streptomyces colonies in the rhizosphere bacteria of Nandi No.4 Increased by112%,and the proportion of Flavisolibacter colonies increased by 96%compared with that of the control group.These colonies may promote the absorption of Cd by plant roots,and deserve further selection of tolerant strains.PICRUSt prediction software was introduced to analyze the bacterial community function of Miscanthus rhizosphere,and the results indicated that the rhizome soil samples of different varieties of Miscanthus presented a function richness in 24 gene function families,including amino acid transportation and metabolism,cell wall/cell membrane/membrane structure biosynthesis,signal transduction mechanism,energy generation and conversion.The predicted gene dosage trend of gene function families was Nandi No.3>Nandi No.4>Xiangmang No.1>Xiangza No.1>Wujie No.1.