| Explosives such as HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine), and TNT (2,4,6-trinitrotoulene) are often found in soil and groundwater from ammunition plants and firing ranges. The research objectives were to determine the toxicity and transformation of HMX by hybrid poplar (Populus deltoides x nigra DN34) cuttings, to investigate the behaviors of the explosives in leaf and root tissues in aqueous phases, to examine the relationship between an endophytic bacteria and plants in the degradation and mineralization of explosives, and to investigate the localization of explosives and endophytes in plant tissues using immunochemistry and in situ hybridization.; HMX was taken-up by poplar cuttings from hydroponic solutions in long term experiments (65 days) without evidence of toxicity. HMX was not toxic to actively-growing hybrid poplar cuttings even under saturated conditions. Seventy percent of 14C-HMX taken by poplars was translocated and accumulated in leaves, and no metabolites were observed during a 65 day exposure using radiochromatography of plant tissue extracts.; Most radioactivity remained in root tissues for 14C-TNT, but in leaves for 14C-RDX and 14C-HMX. Radiolabel recovery of TNT and HMX was over 94%, but that of RDX decreased over time, suggesting loss of volatile products. A considerable fraction (45.5%) of radioactivity taken up by whole plants exposed to 14C-HMX was released into deionized water mostly as parent compound after 5 days of leaching. About a quarter of radioactivity (24.0%) and 1.2% were leached for RDX and TNT, respectively, mostly as transformed products. In the case of root tissues, the amount of radioactivity released was not significant.; Methylobacterium populum, an endophytic bacteria isolated from hybrid poplar was able to degrade and mineralize HMX and RDX by 55--58%. It transformed TNT without mineralization. It was unclear whether the plant or the bacteria caused mineralization, or both, or whether they work symbiotically.; Nonspecific binding of an RDX antibody and a DNA probe in plant tissues prevented determination of the exact location of the explosive and the endophyte in plant cells. |
