The Study On Plant Growth Promoting Rhizobacteria And Its Promoting Functions Towards The Growth And Development Of Phragmites Australis

Reed wetlands are important ecosystems with high economic ecological value.In recent years,Reed wetland of Liaohe River estuary has severely degenerate,biomass has significantly reduced and the ecological function markedly decreased.In order to Increase content of N、P in soil,improve the microhabitats of wetland,and promote the growth of reed,this research is aimed at researching and develop the plant growth promoting rhizobacteria(PGPR) of reed and exploring its influence to reed.Phosphate-solubilizing bacteria and free-living azotobacter are the important components of PGPR.They can transform P which can’t be used by plants to available P, and supply plants with N by Bio-nitrogen fixation.In this research,Monkina organic medium and Ashby medium are used to isolate and select 3 strains of Phosphate-solubilizing bacteria(P1、P2、P3) and free-living azotobacter(N1、N2、 N3) from the soil of Reed wetlands of Liaohe River estuary.They are inoculate to liquid medium to detect content changes of PO43- and NH3-N.After 7 days,the average concentration of dissolved PO43- in PKO liquid medium [Ca3(PO4)2 as Phosphorus source] is 95.2mgL-1,and the Phosphorus-solubilizing rate is 23.8%.Among them,P2 has the strongest Phosphate-solubilizing ability,whose solubilizing rate is 26.35%; The average concentration of dissolved PO43- in Monkina liquid medium (lecithin as Phosphorus source] is 5.87mg·L-1,and the Phosphorus-solubilizing rate is 65.2%.Among them,P3 has the strongest Phosphate-solubilizing ability.whose solubilizing rate is 73.4%; The average concentration of ammonia in Ashby liquid medium is 0.88 mg·L-1.Among them,N2 has the strongest nitrogen-fixation ability,whose ammonia concentration is 0.93 mg·L-1.Meanwhile,by planting Phragmites australis.indoor,its growth status and soil fertility have been monitored.The results show that after 35 days,compared with control group,the average plant height and biomass of experimental group(fertilizing bacterial manure) increase 8% and 50%.Soil fertility and activity is obviously improved:the content of available nitrogen、phosphorus and the activity of urease% phosphatase microbe respectively increase 27%、60%、60%、66% and 23%.In addition,3 strains of bacteria can secrete plant growth hormone(IAA).By strain identification,These 3 strains of phosphate-solubilizing bacteria are Bacillus megaterium、Bacillus aquimaris and Pseudomonas plecoglossicida; nitrogen-fixation bacteria are Pseudomonas brassicacearum、Sphingomonas mali and Enterobacter asburiae.Combined with the study results and some related literature,These species have a certain phosphorus solubilizing, nitrogen fixation ability, but also have a variety of functions such as plant biocontrol, growth-promoting,pollution gradation.Based on the technique of PCR-DGGE,soil microbial populations has been analyzed.The results indicate that after fertilizing bacterial manure.the PGPR can exist stably and also be dominant populations in soil.The diversity of soil bacteria is increased and the original soil microbial communities are not interfered by the PGPR.We conclude that these phosphate-solubilizing bacteria and free-living azotobacter have significant effect on reed growth-promoting.but also have a great potential to improving the quality of reed and community restoration of reed.It provides us with theoretical and practical basis for producing PGPR preparation.