GERMINATION AND SEEDLING DEVELOPMENT OF SWITCHGRASS AND SMOOTH BROMEGRASS EXPOSED TO 2,4,6-TRINITROTOLUENE

It is estimated that explosives contaminate approximately 0.82 million cubic metres of soil at former military installations throughout the US; major contaminants often include 2,4,6-trinitrotoluene (TNT) and i ts degradation products. At some sites, phytoremediation may be a viab le option to incineration or other costly remediation treatments. Gras ses may be particularly suited for remediation because of their growth habit and adaptability to a wide range of soil and climate conditions . We characterized the effects of TNT on germination and early seedlin g development of switchgrass and smooth bromegrass to evaluate their p otential use on contaminated sites. Switchgrass and smooth bromegrass seeds were germinated in nutrient-free agar containing 0 to 60 mg TNT litre(-1). Smooth bromegrass germination decreased as TNT concentratio n increased, while switchgrass germination was unaffected by TNT. Conc entrations up to 15mg TNT litre(-1) did not affect switchgrass root gr owth rate, but bromegrass root growth was reduced at TNT concentration s above 7.5mg litre(-1). At 7.5mg TNT litre(-1), however, shoot growth rate was reduced in both species. Examination at 20-fold magnificatio n revealed switchgrass radicles were unaffected by TNT, while smooth b romegrass radicles appeared slightly swollen. Results indicate switchg rass is more tolerant of TNT than smooth bromegrass, but the establish ment of both species may be limited to soil containing less than 50 mg kg(-1) of extractable TNT. (C) 1998 Elsevier Science Ltd. All rights reserved.