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Oxalate secretion by ectomycorrhizal Paxillus involutus is mineral-specific and controls calcium weathering from minerals

par Schmalenberger, Achim;Duran, A;Bray, A.;Bridge, Jonathan;Bonneville, Steeve ;Benning, Liane G;Romero-Gonzalez, Maria E;Leake, Jonathan R;Banwart, Steven A
Référence Scientific Reports, 5, 12187
Publication Publié, 2015

Article révisé par les pairs

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Résumé :

Trees and their associated rhizosphere organisms play a major role in mineral weathering driving calcium fluxes from the continents to the oceans that ultimately control long-term atmospheric CO2 and climate through the geochemical carbon cycle. Photosynthate allocationto tree roots and their mycorrhizal fungi is hypothesized to fuel the active secretion of protons 35 and organic chelators that enhance calcium dissolution at fungal-mineral interfaces. This was tested using 14CO2 supplied to shoots of Pinus sylvestris ectomycorrhizal with the widespread fungus Paxillus involutus in monoxenic microcosms, revealing preferential allocation by the fungus of plant photoassimilate to weather grains of limestone and silicates each with a combined calcium and magnesium content of over 10 wt.%. Hyphae had acidic surfaces and 40 linear accumulation of weathered calcium with secreted oxalate, increasing significantly in sequence: quartz, granite < basalt, olivine, limestone < gabbro. These findings confirmed the role of mineral-specific oxalate exudation in ectomycorrhizal weathering to dissolve calcium bearing minerals, thus contributing to the geochemical carbon cycle.