A comparative study was conducted on the effects of different concentrations (10-1-10-6) of the plant growth regulator GA3 and PIX on the bacterial population, growth rate, pH, and microstructure of Rhizobium fredii (GIM 1.227) and Bradyrhizobium japonicum (GIM 1.94). The results showed that the bacterial population, growth rate, pH value and relative expression of nodA and nodD of R. fredii and B. japonicum were increased, accelerated, reduced and up-regulated respectively, when the GA3 concentration in the medium was 10-3; however, the bacterial population, growth rate, pH value and relative expression of nodA and nodD of R. fredii and B. japonicum were decreased, decelerated, increased and down-regulated respectively, when the PIX concentration in the medium was 10-2. The microstructure of Rhizobium was altered by the plant growth regulator.
Rhizobium fredii, Bradyrhizobium japonicum, Plant growth regulators, character of Rhizobium, nod gene
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