Symbiosis with Astraeus hygrometricus upregulates cesium and potassium uptake by Pinus densiflora seedlings

After the Fukushima Daiichi Nuclear Power Plant accident in March 2011 in Japan, high activity levels of radiocesium have been reported in wild mushrooms of ectomycorrhizal (EM) fungi. As EM fungal species form symbiotic associations with woody plants, we examined the effect of symbiosis by Astraeus hygrometricus, an EM fungus, on the uptake of cesium (Cs) and potassium (K) by Pinus densiflora seedlings under different levels of K and Cs in the soil in a pot culture. The pine seedlings exhibited enhanced growth due to the symbiosis with A. hygrometricus. The symbiosis with A. hygrometricus significantly increased the Cs and K concentrations of pine seedlings. Cultivating EM seedlings lowered exchangeable K in the soil, although exchangeable Cs did not significantly change. Furthermore, K addition suppresses the Cs absorption of P. densiflora seedlings irrespective of their association with EM fungi.