Effects Of Wetland Rhizosphere Microorganisms On Phosphorus Transformation And Release And Plant Uptake

Wetland plants have a strong accumulation of phosphorus(P),which can effectively remove phosphorus in the environment.However,most forms of phosphorus in the environment can not be directly uptake by plants,and only after decomposition and transformation into available phosphorus can they be absorbed by plants.Therefore,it is a very important basic research work to understand the effect of the transformation and release and plant absorption of phosphorus on the rhiz osphere microorganisms in this process,which can provide the basis for further clarifying the mechanism of phosphorus cycling in wetland,strengthening the absorption of phosphorus and the control of phosphorus contamination in the water ecosystem.The wetland plants in Tianyin Lake(Nanjing,China)and their rhizosphere microorganisms were selected for the research.The diversity of rhizosphere microorganisms in typical wetland plant Acorus calamus was analyzed by high-throughput sequencing.The effects of rhizosphere microbial communities on the transformation of phosphorus and plant uptake by the rhizosphere as a whole are studied by removing and preserving rhizosphere microorganisms.Rhizosphere microorganisms were extracted and purified from the rhizosphere of Acorus calamus,Iris and reed with the general medium of bacteria,and the phosphorus release ability of the extracted strains was tested,and the high efficiency phosphate solubilizing bacteria were screened.Through the determination of phosphorus content in water,plant growth and phosphorus content in the plant,the effect of enhanced phosphorus removal by various high efficiency phosphate solubilizing bacteria was studied.The main innovative research results are as follows: High-throughput sequencing analysis revealed that the most aboundant domain in the studied wetland rhizosphere was bacteria,followed by eukaryotes,the least was archaea.The most bacteria were Acidobacteria and Proteobacteria,which accounted for 34.94% and 34.19% respectively.The most aboundant species of fungi were Sordariomycetes,accounting for 37.06%.An ammoxidation archaea named Candidatus Nitrosoarchaeum was the most aboundant in archea,accounting for 48.07%.They are obviously predominance.The rhizosphere microbial communities in the wetland could promote phosphorus uptake by plants,and total phosphorus of the root,stem and leave of the plants that with rhizospheric microorganisms increased more after culture.The available phosphorus,insoluble inorganic phosphorus and organic phosphorus in water can be transformed and plant absorption could be promote by the rhizosphere microbial communities,and further promoted the removal of total phosphorus in water.Inorganic phosphorus(P)-solubilizing bacteria(IPS B)and organic P-mineralizing bacteria(OPMB)were isolated rhizosphere soil of the wetland.The solubilizing of inorganic phosphorus was the major contribution to phosphorus availability,since the isolated bacteria released much more available phosphorus from inorganic tricalcium phosphate than lecithin.The same strain had different release effects on inorganic insoluble phosphorus and organic phosphorus,indicating that the factors affecting the dissolution and release of organic phosphorus and inorgani c phosphorus were different.In the medium of tricalcium phosphate,the highest short-term phosphorus solubilizing and release rate was 0.53 mg·L-1·h-1 in 96 hours,and the highest phosphorus solubilizing and release rate was 0.38 mg·L-1·h-1,0.50 mg·L-1·h-1 and 0.52 mg·L-1·h-1 in 10 days,respectively.The amount of dissolved phosphorus released by different strains in different media was diverse.In organic phosphorus medium,the highest short-term phosphorus release rate was 0.029 mg·L-1·h-1 in 96 hours and 0.0078 mg·L-1·h-1 in 10 days.The bacteria released the most dissolved phosphorus which was 125.88 mg·L-1 from tricalcium phosphate medium in 10 days,while the bacteria released the most dissolved phosphorus from organic phosphorus medium among the isolates,with a concentration of 1.88 mg·L-1 in 10 days.The bacteria with fastest short-term phosphorus release rate screened from the rhizosphere of Acorus calamus was identified as Pseudomonas sp.and the bacteria released the most dissolved phosphorus screened from the rhizosphere of reed was identified as Pseudomonas knackmussii.Different phosphate solubilizing bacteria had different effects on phosphorus content in water and phosphorus uptake by wetland plants.M24 and M25,which had the highest phosphate solubilizing capacity,were the most effective in removing phosphorus and promoting phosphorus uptake in plants.Phosphorus uptake by plants is mainly reflected by the growth of leaves and the increase of phosphorus content.The removal rate of total phosphorus in water increased with the raise of amount of phosphate solubilizing bacteria seeded on the rhizosphere of the plants,and the increase of phosphorus content in each part of the plant was more obvious.The p H variation was small during the incubation,which was ranged from 6.7~ 7.1.This study provides important basic data and conclusions for the use of highly effective phosphate solubilizing bacteria to enhance plant absorption of phosphorus and improve the phosphorus removal efficiency of wetlands.