Stimulation of heterotrophic dinitrogen fixation in barley root association by the herbicide pendimethalin and its metabolic transformation by Azotobacter SPP

摘要: Abstract Pendimethalin [N-(l-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzamine] at normally applied concentrations stimulated root associated nitrogen fixation activity of young barley seedlings in a neutral alluvial loam soil, as measured by excised-root acetylene reduction assay. From 3- to 7-fold increases excised C2H2-reduction (ARA) were obtained with 3–5 kg a.i. ha−1 15–35 days age seedlings. The stimulatory response declined and higher the herbicide. Root-associated aerobic microaerophilic N2-fixing bacterial populations registered highly significant increase corresponding ARA herbicide but not much soil. Isolates ofAzolobacter vinelandu Azospirillum lipaferum from herbicide-treated rhizosphere showed vitro tolerance high N-free media. Azolobacler isolate utilized pcndimethalin C source (o fix N2 pure culture equal efficiency that mannitol. mctabolically-degraded pendimcthalin several products including N-dcalkylated product. 2.6-dinitro-3,4-dimcthylbenzamine. property utilization for was also available an A. chrootoccum without prior exposure