Investigation On Stress Resistance,Rhizosphere Soil Enzyme Activity And Bacterial Community Of Two Wetland Plants

With the rapid growth of the global population and fast economic development,as well as the continuous advancement of urbanization and industrialization,human demand for water resources is increasing.Meanwhile,more water pollution is inevitable.The original Sewage treatment technology can no longer meet people's growing needs.Constructed wetlands are widely used due to their low energy consumption,low cost,low-level construction,and easy operation.Previous researches on constructed wetlands often focused on the selection and matching of suitable wetland plants in order to maximize the effect of plants on sewage purification in constructed wetland systems.There are few studies on the stress resistance of wetland plants under specific geological conditions and the complete cycle system of "plant-soil-microorganism".Therefore,this thesis collected Phragmites communis,Zizania aquatica and its rhizosphere soil from Xiangfen County Wastewater Treatment Plant in Shanxi Province,and investigated "plant-soil-microbial system" to make a theoretical basis for screening suitable wetland plants in Shanxi-like regions.In this study,we collected Phragmites communis,Zizania aquatica leaf and root samples from wetland and unstressed control soil,measured the contents of chlorophyll,soluble protein,malondialdehyde(MDA),superoxide dismutase(SOD),and cytochrome oxidase P450(CYP450),nitrogen,phosphorus and potassium.And we collected plant-free wetland soil and wetland plant rhizosphere soil,and measure p H value,heavy metal content,urease(UE)content,alkaline phosphatase(ALP)content,microbial biomass carbon(SMBC),and microbial biomass nitrogen(SMBN),and used16 S r RNA gene high-throughput sequencing to analyze the bacterial community structure in different groups.Results found that:(1)the contents of chlorophyll,soluble protein,and MDA in leaves of wetland Phragmites communis and Zizania aquatica increased compared with the control group(increased from 23.56 mg / g,15.89 mg / g;0.98 g / L,1.43 g / L;0.11 nmol /mg protein,0.29 nmol / mg protein to 44.27 mg / g,33.17 mg / g;2.10 g / L,2.61 g / L;0.7 nmol / mg protein,1.01 nmol / mg protein),and SOD activity,soluble protein content in roots,and CYP450 activity in roots increased significantly compared with the control group(increased from 40.32 U / mg protein,32.68 U / mg protein;0.09 g / L,0.38 g / L;176.98 U / mg protein,39.96 U / mg protein to 54.73 U / mg protein,43.79 U / mg protein;0.11 g /L,0.45 g / L;361.46 U / mg protein,50.79 U / mg protein);compared with Zizania aquatica,wetland Phragmites communis had higher chlorophyll levels,lower MDA content,higher SOD activity,and increased CYP450 activity,indicating that both Phragmites communis and Zizania aquatica are good artificial wetland restoration plants,and Phragmites communis' s resistance to stress is relatively better than Zizania aquatica.(2)The soil heavy metal content did not exceed the Chinese soil standard.Compared with Zizania aquatica,Phragmites communis also had higher soil enzyme activities,SMBC and SMBN.It indicates that microorganisms and their metabolites can adsorb and transform heavy metals,and Phragmites communis can better promote nutrient accumulation,which is beneficial to plants and microorganisms grow.(3)The bacterial abundance,abundance,and alpha diversity of the microorganisms in the Phragmites communis rhizosphere soil were the highest.Among them,Gp6 was the most abundant bacteria in the Phragmites communis rhizosphere soil and control soil,while the most abundant bacteria in the Zizania aquatica rhizosphere soil were Gemmatimonas.Redundant analysis(RDA)found that the bacterial community in Phragmites communis rhizosphere soil was mainly affected by a positive correlation with arsenic,nickel or SMBC.The bacterial community in Zizania aquatica rhizosphere soil was positively correlated with Cd,ALP,Pb,and UE,respectively,the bacterial community in the control group was mainly affected by a negative correlation with p H.Based on cluster of orthologous group(COG)pathway analysis data,the main functions of the dominant bacteria Gp6 and Longilinea in the Phragmites communisrhizosphere soil were involved in the metabolism of many carbohydrates and the carbon cycle.In general,Phragmites communis is a recommended species for wastewater treatment wetland systems in Shanxi Province.Special enzymes and dominant bacteria in the rhizosphere soil of plants have an apparent ability to remove organic pollutants.Besides,in the wetland wastewater treatment system,the influence of environmental factors on rhizosphere bacteria and the synergistic effect of Phragmites communis and dominant bacteria should be considered.