Effects Of AM Fungi And Bacillus On The Competitive Growth Of Flaveria Bidentis Under Different Soil Nutrients

Flaveria bidentis can change the soil microbial community structure and accumulated specific AM fungi and plant growth-promoting rhizobacteria in the rhizosphere,which benefit its successful invasion.To explore the roles of AM fungi and bacillus accumulated in the rhizosphere soil of F.bidentis in competition between Flaveria bidentis and native plant the pot experiment was carried out.Our previous study showed that Brevibacterium frigoritolerans,Bacillus megaterium and Rhizophagus intraradices were the dominant bacillus and arbuscular mycorrhizal fungi in the rhizosphere soil of F.bidentis respectively.The effect of B.frigoritolerans(or B.megaterium)and R.intraradices on competition between F.bidentis and native Eclipta prostrate were carried out on different nutrient levels.The results are listed as follows:The effect of R.intraradices and B.frigoritolerans on the competition between F.bidentis and E.prostrate was carried out to explore their roles in the competition.Competition did not benefit the growth of both F.bidentis and E.prostrate under low nutrient levels.R.intraradices shifted the competitive relationship between F.bidentis and E.prostrate.R.intraradices promoted the competitive growth of F.bidentis,while inhibited that of E.prostrate.B.frigoritolerans may promote the growth of F.bidentis and E.prostrata by activating soil nutrients,but it cannot change the competition relationship between F.bidentis and E.prostrata.In the competitive growth of F.bidentis and E.prostrata,R.intraradices changed the competitive relationship between F.bidentis and E.prostrate.R.intraradices promoted the competitive growth of F.bidentis and inhibited the competitive growth of E.prostrata.The synergistic effect of both B.frigoritolerans and R.intraradices not only increased the biomass of F.bidentis,but also enhanced the competitiveness of F.bidentis.B.frigoritolerans has the ability to promote their growth by activating soil nutrient,whereas it cannot change their competitive relationship.The synergistic effect of B.frigoritolerans and R.intraradices increased the biomass of F.bidentis and enhanced its competitive ability.The effect of R.intraradices and B.megaterium on the competition between F.bidentis and E.prostrate was carried out both under low and high nutrient levels.Different soil nutrient conditions have different effects on the competitive growth of F.bidentis and E.prostrata.In low-nutrient soils their competition was not conducive to their growth,while in rich-nutrient soils the competition promoted the growth of F.bidentis and inhibited the growth of E.prostrata.The function of B.megaterium may be different role in the competitive growth of F.bidentis under different soil nutrient levels.In low-nutrient soils,B.megaterium promoted the absorption of F.bidentis and E.prostrata by activating soil nutrients,but it did not change the competitive relationship between F.bidentis and E.prostrata.However,in rich nutrient soil,B.megaterium altered the competitive ability of F.bidentis and E.prostrate.B.megaterium promoted the competitive growth of F.bidentis and inhibited that of E.prostrata.Under different soil nutrient levels,the function of R.intraradices was to promote the absorption of nutrients by F.bidentis and promoted its competitive growth.The synergistic effect of B.megaterium and R.intraradices led to a wide range of environmental adaptability of F.bidentis by changing soil microbial structure and function.The pot experiment was constructed to explore the role of R.intraradices and B.megaterium in competitive growth of F.bidentis under different soil nitrogen levels.With the increase of nitrogen concentration,the net photosynthetic rate,total nitrogen,total phosphorus and root growth characteristics of F.bidentis and E.prostrata increased significantly in both the monocultures and the mixtures.There were significant increases in the biomass of F.bidentis and E.prostrata.However,competition had a negative effect on the growth of both F.bidentis and E.prostrata.B.megaterium had no effect on the competitive growth of F.bidentis,but it decreased the negative effect on the E.prostrata.With the increase of nitrogen concentration,the negative effect of B.megaterium on the E.prostrata decreased gradually.R.intraradices promoted competitive growth of F.bidentis regardless of nitrogen levels.With the increase of nitrogen concentration,the colonization rate of R.intraradices decreased significantly,the positive effect on F.bidentis and the negative effect on E.prostrata were decreased.The synergistic effect between B.megatreium and R.intraradices promoted the competitive growth of F.bidentis and inhibited the competitive growth of E.prostrata.With the increasing of nitrogen concentration,the negative effect on E.prostrata decreased gradually.