Scanning Microscopy


Wood decay experiments using red spruce wood resting on moist soil were conducted to discern temporal and spatial patterns of calcium oxalate (CaOx) crystal production by three species of fungi over the course of decay. All three species produced crystals of calcium oxalate dihydrate, but not monohydrate, in and on wood. Over the course of decay, the production of CaOx crystals was shown to be heterogeneous in both space and time. The relative quantity, morphology and longevity of CaOx crystals varied among species. Gloeophyllum (G.) trabeum produced substantial quantities of "free" crystals; Fomitopsis (F.) pinicola produced encrusting crystals; and Trichaptum (T.) abietinum produced adhering crystals and druses. Paramorphic corrosion of crystals was observed most frequently in the brown rot fungus G. trabeum and not at all in the white-rot fungus T. abietinum. Often associated with crystal precipitations was the production of crystal surface-obscuring extracellular matrix. All the species observed produced CaOx crystals more consistently in or on soil than in wood. The study of crystal production patterns and crystal morphologies could yield important information about the microenvironmental conditions in wood during biodegradation and the mechanisms by which wood decay fungi decompose lignocellulose.

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