Abstract
Timbers in cooling towers are mainly attacked by soft rot causing fungi which belong to Ascomycetes and Deuteromycetes. The basidiomycete Physisporinus vitreus degraded water-saturated limber as fibrous white-pocket rot in a cooling tower in which water treatment had been changed from chlorine to ozone. In the laboratory, the fungus revealed a remarkable wood decay pattern. In crosswise piled. water-saturated pine specimens it attacked only those parts not surrounded by air. The decay occurred as small longish delignified white pockets, preferentially in the earlywood. Transmission electron microscopy of unstained sections showed some electron density in the hyphal extracellular layer and in the wood cell wall beneath a hypha. Contrasted with KMnO 4 staining these regions became more pronounced which may indicate presence of lignin depredation products. UV-microspectrophotometry of these areas exhibited an increased absorbance. Many decay pockets were black due to manganese (Mn) deposits. Mn determination by inductively coupled plasma emission (ICP) revealed up to 518 ppm Mn. TEM/EDXA showed Mn deposits in the hyphal extracellular layer, on the cell wall surface and in the inner S 2 layer beneath a hypha. The Mn may he related to the lignin attacking peroxidases.
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