Fate of 2,4,6-trinitrotoluene in axenic sand culture systems containing smooth bromegrass

Plants have the potential to metabolize the munition 2,4,6-trinitrotoluene (TNT) in contaminated soils, sediments, and natural waters. However, microb ial interference must be eliminated to demonstrate an intrinsic capacity fo r the metabolism of TNT by plants. An axenic sand culture system for smooth bromegrass (Bromus inermis Leyss) was established to investigate the influ ence of TNT on smooth bromegrass growth and metabolism Shoot length growth was inhibited by 40% after 14 d of exposure to TNT at 36 mg/L in the sand s olution, whereas photosynthetic and respiration rates were similar to contr ols. Addition of [C-14]-labeled TNT to the system resulted in the roots con taining 21.3% and the shoots containing 3.8% of the radioactivity. The [C-1 4]TNT in media that contained plants was reduced about 50% compared to medi a without plants. Trace amounts (0.03%) of the initial [C-14]TNT was conver ted to (CO2)-C-14 during a 5-d incubation period. The TNT and its metabolit es were observed in root and shoot extracts by radiochromatographic analysi s. The major TNT metabolites identified were 2-amino-4,6-dinitrotoluene and 4-amino-2,6-dinitrotoluene. Previous exposure of the plants to TNT did not increase TNT metabolism or prevent reduction of shoot length growth. From these results we concluded that smooth bromegrass is capable of taking up a nd metabolizing TNT.