Element distribution in fruiting bodies of Lactarius pubescens with focus on rare earth elements

During growth and senescence, fungal fruiting bodies accumulate essential and non-essential elements to different extent in their compartments. This study bases on a dataset of 32 basidiocarps of the ectomycorrhizal Lactarius pubescens sampled in a former U mining area. Statistical analyses were combined with rare earth element (REE, La-Lu) patterns to study the element distribution within sporocarp compartments and between three different age classes. For this purpose, fruiting bodies were separated into stipe, pileus trama, pileipelles and lamellae, dried and digested with HNO₃. While macronutrient (e.g. K, Mg, P, S) contents resemble those of a non-mining affected site, several elements (e.g. Co, Mn) were site-specifically taken up relative to elevated soil contents. With statistics, two main element distribution groups for L. pubescens were revealed: mainly essential (Cu, Mg, Mn, P, S, Zn, Cd, Co, Ni) and mainly non-essential elements (Al, Ca, Fe, Sr, U, REE). The highest REE contents were found in pileipelles and lamellae, corresponding to relatively small cell sizes. Stipes and pileus trama had low REE contents due to their function as transport systems. During growth, light REE (La-Nd) were strongly enriched in lamellae and pileipelles. Middle REE (Sm-Dy) enrichment was found both in soil and fungal biomass. Contents of nutrients decrease with age, while non-essential elements are enriched especially in pileipelles and lamellae. A weak positive Ce anomaly appeared in the bioavailable soil fraction and in the pileipelles of younger individuals. Substrate dependent uptake thus gets reduced with sporocarp senescence, possibly due to redistribution.