| In this paper,based on the Hylotelephium spectabile as the research object,zinc absorption and transport capacity,the physiological and biochemical indexes were determined.The tolerance and enrichment of heavy metal zinc were analyzed.At the same time for Hylotelephium spectabile rhizosphere soil enzyme activity and soil microbial community structure and function diversity were studied under the stress of zinc.Hylotelephium spectabile rhizosphere zinc resistant strains were extracted by conventional approach.The ability of strains to resist zinc were determined,and the effects of the growth and zinc absorption promotion of the strain were also verified by the experiments of applying zinc resistant strains to plants,which provided a good basic data for the screening of zinc resistant plants and zinc resistant strains in the future.The results are as below.The analysis of Hylotelephium spectabile on zinc tolerance results show that strong endurance and recovery ability of this plant under zinc stress were adaptively adjusted by protective enzyme system in the physical.In the process of different concentrations of zn stress,the Hylotelephium spectabile biomass decreased,but the toxicity was reduced by a variety ways such as increasing the activities of antioxidant protective enzyme,stomatal closure,reducing moisture loss,which maked Hylotelephium spectabile has strong resistance ability of zn stress.Although the amount of Hylotelephium spectabile to absorb zinc did not reach the standard of hyperaccumulator,the biomass,zinc content in plant and transport capacity proved that this plants have good tolerance to zinc.Hylotelephium spectabile have a high ornamental value,which has a good prospect for Zn soil remediation and landscaping.The analysis of Hylotelephium spectabile rhizosphere soil enzyme activity under zinc stress results show that soil dehydrogenase,invertase,phosphatase,nitrate reductase and urease activity increased first and then decreased with the increasing of zinc concentration,which proved these five kinds of enzymes were inhibited under high concentration of zinc stress.Dehydrogenase,invertase and phosphatase activities were decreased when the zinc concentration was greater than 800 mg·kg-1,while the activity of nitrate reductase decreased at 160 mg·kg-1,urease at 320 mg·kg-1,and the sensitivity of phosphatase is higher than that of the other four enzymes.The research of differences in metabolic capacity and functional diversity of rhizosphere soil microbial community under zinc stress were carried out by Biolog-Eco method.The metabolic activity of rhizosphere soil microorganism were not significantly inhibited when zinc stress concentration reached 800 mg·kg-1,and the microbial metabolic activity significantly enhanced compared with control group,there is no significant difference between groups of samples of microbial metabolic activity except the sample of 80 mg·kg-1.When zinc stress concentration reached 1 600 mg·kg-1,the metabolic activity of rhizosphere soil microorganism were significantly inhibited.There were differences for ability to use the same carbon source of rhizosphere microorganism under difference zinc concentration stress,and microorganism's ability to use six kinds of carbon source was different in the same zinc concentration stress.Through principal component analysis of the carbon source utilization ability,the D,L-a-phosphoglycerol,D-Xylose/amyl aldehyde sugar and y-hydroxybutyric acid were Hylotelephium spectabile rhizosphere soil microbial community specific utilization of carbon source under zinc stress.Hylotelephium spectabile rhizosphere soil enzyme activity and microorganism abundance were increased with the increasing of Zn2+,there was a significant correlation between them.Therefore,rhizosphere soil enzyme activity and microorganisms functional diversity worked together to make Hylotelephium spectabile strong resistance of zinc.Identification and comparative study of Hylotelephium,spectabile rhizosphere soil bacterial community structure under zinc stress were carried out by Illumiana Mi Sep high throughput sequencing technology.There were no significant difference between rhizosphere bacteria structural diversity in the zinc stress concentration 40?600 mg·kg-1.Soil bacteria species structure had a certain similarity between zinc stress concentration at 320 mg·kg-1 and 800 mg·kg-1,0 mg·kg-1 and 160 mg·kg-1,40 mg·kg-1,80 mg kg-1 and 1 600 mg·kg-1.Soil bacteria are mainly distributed in Proteobacteria,Chloroflexi,Acidobacteria,Actinobacteria,Bacteroidetes,Gemmatimonadetes,Verrucomicrobia,Nitrospirae,Parcubacteria and other kinds of bacteriophyta.Between different treatment group concentration,the proportion of different categories of bacteria was different.But the Proteobacteria in the percentage of each treatment concentrations were highest,which certified that the Proteobacteria was thedominant population.The bacteria of each treatment from the genera classification has mainly Anaerolineaceae,Subgroup-6-norank,Nitrosomonadaceae and Gemmatimonadaceae.The Subgroup-6-norank was a small group composed of six kinds of unknown species.Isolating and screening of Hylotelephium spectabile rhizosphere strains at zinc concentration of 800 mg·kg-1 were carried out,and six kinds of strains were obtained.The strains were identified from three levels of morphology,physio-biochemical characteristics and molecular biology.Comprehensive comparison of the three levels of identification results that Zn1 and Zn4 belong to Stenotrophomonas,Zn2 belong to Xanthomonas,Zn3?Zn5 and Zn6 belong to Enterobacter.The results showed that six strains were isolated and screened from the Rhizosphere Agrobacterium tumefaciens with zinc concentration of 800 mg·kg-1,and the results were as follows:Zn1 and Zn1 Zn4 belongs to the genus Stenotrophomonas;Zn2 belongs to the genus Xanthomonas;Zn3 and Zn5 belong to Enterobacter.Zn6 belongs to Enterobacter.Zn1,Zn2,Zn4,Zn5 and Zn6 had good zinc resistance by the physiological test of the strain under zinc stress.Zn1,Zn4 and Zn5 were strong and adaptable after being transferred to the culture medium.Zn1,Zn4,Zn6 produced more IAA,all strains have the ability of nitrogen fixation,Zn1,Zn4,Zn6 has the ability to dissolve phosphorus.Zn1,Zn4,Zn6 was the strongest r producers of ironophore,Zn5 has a certain capacity of ironophore secretion,and Zn2,Zn3 did not have this capacity.Zn1,Zn2,Zn4,Zn6 could produce a mass of ACC deaminase,but the other strains only produce a very small amount of ACC deaminase,or even could not produce this enzyme.According to the ability of the strain to promote growth,five kinds of strains were selected for backfilling experiment.They were Zn1?Zn2?Zn4?Zn5?Zn6.The results showed that leaf zinc content increased most significantly at Znl,Zn4,Zn6-treated group,which was 29.6%,39.6%and 23.6%higher than that of the control group.Therefore,these three strains were established to improve the tolerance of Hylotelephium spectabile to heavy metal zinc and enhance the capacity of zinc absorption. |
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