Study On Quantity Dynamic Changes Of Rhizosphere Myxobacteria And Its Inductive Effect From Different Allelopathic Rice Accessions Under Stressful Conditions

Allelopathy is a chemical interaction between organisms in which one living plants suppresses the germination,growth of the others by releasing chemicals into the environment.The phenomenon is found in many crop plants,including rice,wheat corn etc.In recent years,plenty of studies had show that plant rhizospheric microorganisms play vital roles in the process,and some microbes function in degradation and transformation of phenolic acids.Numbers of studies have indicated that rice allelopathic potential was enhanced under stressful conditions,which attributed to the enhancement of gene expression level on those relevant to phenolic acids synthesis,following by the increasement of phenolic acids exudates in soil.However,seldom studies focus on whether the growth development and proliferation of some special microbes would be influenced by these phenolic acids.In this research,determination on the dynamic changes of myxobacteria's numbers from different rice accessions under stressful conditions was performed,and the results indicated the mycobacterium quantity was in correlation with phenolic acids concentrations.It was found that the amount of myxobacteria in allelopathic rice PI312777 rhizosohere soil was higher than that of non allelopathic rice Lemont during rice seedling stage,especially when the two rice accessions were exposed to stressful conditions.When the two rice accessions were cultured in high nitrogen content soil,the maximum amount of rhizosphere myxobacteria from allelopathic rice PI312777 showed 10 times higher than that of Lemont in the same stage,and the difference increased to 60 fold when they were in the situation of drought stress.Further,the myxobacteria from allelopathic rice rhizosphere soil were separated by using rabbit dung.Solution of phenolic acids mixture was used to study its inductive effect on myxobacteria;it was found that the amount of myxobacteria was significantly enhanced after inducing by phenolic acid within 24h.The result suggests that some signal substances may released from myxobacteria,and it contributed to the microbes make a great multiplication.The performance resulted in quickly consumption on the nutritional resources and then induction of large group of fruiting body.According to the evaluated result of weed suppression ability from the myxobacteria,it was found that the germination of barnyardgrass was significantly inhibited by myxobacteria,but it took no influence on rice germination.Basing on the studies above,it was concluded that the increasing of phenolic acid from allelopathic rice root under stressful conditions could further affects the growth and proliferation of the characteristic myxobacteria around,and make the microflora largely increased,which in turn could change the soil microenvironment and finally inhibit the barnyardgrass.