IN-VITRO WEATHERING OF PHLOGOPITE BY ECTOMYCORRHIZAL FUNGI .1. EFFECTOF K+ AND MG2+ DEFICIENCY ON PHYLLOSILICATE EVOLUTION

The ways in which ectomycorrhizal fungi benefit tree growth and nutrit ion have not been fully elucidated. Whilst it is most probably due to improved soil colonization, it is also likely that ectomycorrhizal fun gi could be directly involved in nutrient cycling of soil reserves. Th is study assessed access by two species of ectomycorrhizal fungi to so il nonexchangeable K+ reserves. The incubation of ectomycorrhizal fung i in bi-compartment Petri dishes with phlogopite led to cation exchang e reactions and to crystal lattice weathering. Paxillus involutus COU led to irreversible phlogopite transformations, while Pisolithus tinct orius 441 led to reversible ones. Simultaneous depletion in K+ and Mg2 + led to an enhanced weathering of phlogopite by P. tinctorius 441. Th e observation of phlogopite evolution shows that some specific Al3+ im mobilization occurred under P. tinctorius 441. The data suggest that t hese bio-weathering mechanisms could be related to the release of fung al organic acids or other complex forming molecules.