Factors influencing water solubility and plant availability of mineral compounds in the tripartite fairy rings of Marasmius oreades (BOLT.: FR.) FR.

Fairy rings of M. oreades on pasture land were denoted by the dark-green vegetation. Grasses and rooted soils were analyzed to determine the influence of nonsymbiotic fungal mats on plant uptake of (heavy) metals. In soil colonized by M. oreades, degradation of 20-35% of plant roots in the presence of fungal laccase increased the content of dissolved organic carbon (3.74x), hexose sugar (3.75x), NH(3)/NH(4) (+) (5.1x), NO(3) (-) (11.1x), the number of aerobic bacteria (14.4x), and the formation of the phytochelators, oxalic, citric, and malonic acids. Soil pH diminished by 1.5 units mainly due to nitrification and carboxylic acid production. Although the solubility of trace elements increased (6.1x), plant roots had the same trace metal content as control plants, whereas the shoot content in Al, Cr, Fe, Ni, and Ti decreased by more than 50% due to inhibited root-to-shoot transfer. It is concluded that M. oreades and its associated bacteria increase the solubility of soil minerals significantly, but make them, due to presumed particularities in their complexation, less plant available and less re-complexable for the translocation into the plant vascular system. ((c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim).