Influence of the nutritional mechanism of fungi (mycorrhize/saprophyte) on the uptake of radionuclides by mycelium

Abstract

Summary Field studies have shown that the uptake of radionuclides by fungi depends on its nutritional mechanism (mycorrhizal or saprophytic), but this fact is only fully demonstrated for radiocaesium. To extend this conclusion to other radionuclides likely to be released in semi-natural ecosystems, we carried out a series of experiments under controlled laboratory conditions of the growth of mycelium of mycorrhizal and saprophytic fungi (Pleurotus eryngii and Hebeloma cylindrosporum respectively) on liquid culture media containing known added activities of 60Co, 85Sr, and 134Cs. The radionuclide incorporated most efficiently into Pleurotus eryngii was 134Cs, and into Hebeloma cylindrosporum was 60Co. For 134Cs and 85Sr, we also analysed the influence that the content of the chemically analogue elements K and Ca respectively in the culture medium had on its uptake. For both species, the uptake of 134Cs is not correlated with the content of K in the media, but it is the uptake of 85Sr increasing with it. These results seem to be independent of the nutritional mechanism. The influence of linearity in the uptake of 134Cs and 85Sr with increasing concentrations of Cs and Sr in the culture medium was also studied. For Pleurotus eryngii it was observed a decrease in the uptake of 134Cs with increasing Cs content in the medium, and an increase in the uptake of 85Sr with increasing Sr content in the medium.