2.3 Indole-3-acetic acid production(11 pt)
Pure bacterial cultures were inoculated into Tryptic soy broth (Criterion,USA) with different concentrations of L-tryptophan and incubated in darkness at 37 c for 24 hours under static conditions. The cultures were then harvested and centrifuged at 10,000 rpm for 10 minutes. To determine IAA,500 of Salkowski reagent (14) was added to 500 ul of supernatant. The absorbance was measured at 535 nm after 30 minutes of incubation. IAA concentrations were determined from the three replicates. Means+SD were given. The statistical analyses were carried out using one-way ANOVA and Kruskal-Wallis test with the program STATGRAPHICS 3.0.