Effect Of Plant Growth Regulators On Growth And Functions Of Rhizobium Fredii And Bradyrhizobium Japonicum

In order to explore the effect of plant growth regulators (PGRs) on physical and chemicalproperties of rhizobium, a comparative study was conducted on the effects of differentconcentrations (10-1-10-6v/v) of the plant growth regulators GA3and PIX on the bacterialpopulation, growth rate, pH, nitrogenase activity, microstructure, functional gene andproteins expression of Rhizobium fredii and Bradyrhizobium japonicum. Then the effect ofRhizobium fredii and Bradyrhizobium japonicum under PGRs on nodule number andnitrogenase activity of soybean root, the content of nitrate-nitrogen, free amino acid, nitratereductase and yield components, yield and nitrogen content of grain was measured insoybean. The results as follow:The bacterial population, growth rate, pH value and nitrogenase activity of R. fredii and B.japonicum were increased, accelerated, reduced and inhibited respectively, when the GA3concentration in the medium was10-3v/v, however,those of R. fredii and B. japonicum weredecreased, decelerated, increased and promoted, when the PIX concentration in the mediumwas10-2v/v. The microstructure of R. fredii and B. japonicum was altered by the plantgrowth regulators.The relative expression of nodA and nodD of R. fredii and B. japonicum wereup-regulated, but the relative expression of nifA, nifH and fixA gene of those weredown-regulated respectively when the GA3concentration in the medium was10-3v/v;however, the status was diverse when the PIX concentration in the medium was10-2v/v byreal time-PCR.Several proteins were down-regulated in ten proteins of differential expression of B.japonicum under GA3condition by two-dimensional electrophoresis. However, fifteenproteins were up-regulated in seventeen proteins of differential expression of B. japonicumunder PIX condition, including four specific expression proteins by two-dimensionalelectrophoresis.The number of nodules and nitrogenase activity of soybean root were increased andinhibited when soybean were inoculated with R. fredii and B. japonicum under GA3condition respectively, however, those of R. fredii and B. japonicum were decreased andpromoted when soybean were inoculated with R. fredii and B. japonicum under PIXcondition. Meanwhile, the content of nitrate-nitrogen, free amino acid, nitrate reductase andyield components, yield and nitrogen content of grain were increased and improved insoybean which were inoculated with both R. fredii and B. japonicum under GA3and PIX.