SR-90 UPTAKE BY PINUS-PONDEROSA AND PINUS-RADIATA SEEDLINGS INOCULATED WITH ECTOMYCORRHIZAL FUNGI

Strontium-90 (Sr-90) is a radionuclide characteristic of fallout from nuclear reactor accidents and nuclear weapons testing. Prior studies have shown that Pinus ponderosa and P. radiata seedlings can remove appreciable quantities of Sr-90 from soil and store it in plant tissue. In this study, we inoculated P. ponderosa and P. radiata seedlings with one of five isolates of ectomycorrhizal fungi. Inoculated and noninoculated (control) seedlings were compared for their ability to remove Sr-90 from an organic growth medium. Seedlings were grown in a growth chamber in glass tubes containing 165 cm3 of sphagnum peat moss and perlite (1:1 (v/v)) and, except in the controls, the fungal inoculum. After 3 months, 5978 Bq of Sr-90 in 1 ml of sterile, distilled, deionized water was added. Seedlings were grown for an additional month and then harvested. P. ponderosa seedlings with ectomycorrhizae accumulated 3.0-6.0% of the Sr-90; bioconcentration ratios (Bq Sr-90 cm-3 plant tissue/Bq Sr-90 cm-3 growth medium) ranged from 98-162. Ectomycorrhizal P. radiata seedlings accumulated 6.0-6.9% of the Sr-90; bioconcentration ratios ranged from 88-133. Nonmycorrhizal P. ponderosa and P. radiata seedlings accumulated only 0.6 and 0.7% of the Sr-90 and had bioconcentration ratios of 28 and 27, respectively. Ectomycorrhizal P. ponderosa and P. radiata seedlings are able to remove 3-5 times more Sr-90 from contaminated soil than seedlings without ectomycorrhizae.