Transfer of radioactive cesium and potassium, and water into the fruiting bodies of oyster mushrooms

Radioactive cesium (Cs) accumulates in mushrooms, but the underlying mechanism remains unclear. Investigating Cs transfer from contaminated wood to a mushroom's fruiting bodies may help prevent radioactive Cs accumulation in mushrooms. Here, a culturing test of a saprophytic mushroom (Pleurotus ostreatus) in a wood sawdust-based medium containing radioactive Cs was conducted to understand ¹³⁷Cs, ⁴⁰K and water transfer during mycelial growth and fruiting body development. The ¹³⁷Cs concentration in the fruiting body was determined by the total ¹³⁷Cs concentration in the medium and not by the difference in the local ¹³⁷C concentration. In other words, ¹³⁷Cs was absorbed from the entire medium. Although ¹³⁷Cs was passively transferred from the medium to the fruiting body, ⁴⁰K was actively transferred. The amount of water in the medium increased because of the decomposition of organic matter by the fungus, more water was transferred to the fruiting body as it developed. The easy transfer of ¹³⁷Cs to the fruiting body might be because of the easy dissolution of ¹³⁷Cs from the solid phase of the medium into the liquid phase. The Cs dissolved in the liquid phase of the medium may be passively taken up by the mycelium and transferred to the fruiting body along with the movement of water.