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The present work investigates environmental effects on the growth of fungal colonies of P. vitreus by using a lattice-free discrete modelling approach called FGM (Fuhr et al. (2010), arXiv:1101.1747), in which hyphae and nutrients are considered as discrete structures. A discrete modelling approach allows studying the underlying mechanistic rule concerning the basic architecture and dynamic of fungal networks on the scale of a single colony. By comparing simulations of the FGM with laboratory experiments of growing fungal colonies on malt extract agar we show that combined effect of temperature, pH and water activity on the radial growth rate of a fungal colony on a macroscopic scale may be explained by a power law for the growth costs of hyphal expansion on a microscopic scale. The information about the response of the fungal mycelium on a microscopic scale to environmental conditions is essential to simulate its behavior in complex structure substrates such as wood, where the impact of the fungus to the wood (i.e. the degradation of bordered pits or the creation of bore holes and cavities) changes the local environmental condition, e.g. the permeability of the substrate and therefore the water activity level in a colonized wood cell lumen. A combination of diffusion and moisture processes into wood with the FGM may brighten the knowledge about the colonization strategy of P. vitreus and helps to optimize its growth behavior for biotechnological application such as bioincising.

Wood-decay fungi decompose their substrate by extracellular, degradative enzymes and play an important role in natural ecosystems by recycling carbon and minerals fixed in plants. Thereby, they cause significant damage to the wood structure and limit the use of wood as building material. Besides their role as biodeteriorators wood-decay fungi can be used for biotechnological purposes, e.g. the white-rot fungus Physisporinus vitreus for improving the uptake of preservatives and wood-modification substances of refractory wood. Therefore, the visualization and the quantification of microscopic decay patterns are important for the study of the impact of wood-decay fungi in general, as well as for wood-decay fungi and microorganisms with possible applications in biotechnology. In the present work, we developed a method for the automated localization and quantification of microscopic cell wall elements (CWE) of Norway spruce wood such as bordered pits, intrinsic defects, hyphae or alterations induced by P. vitreus using high resolution X-ray computed tomographic microscopy. In addition to classical destructive wood anatomical methods such as light or laser scanning microscopy, our method allows for the first time to compute the properties (e.g. area, orientation and size-distribution) of CWE of the tracheids in a sample. This is essential for modeling the influence of microscopic CWE to macroscopic properties such as wood strength and permeability.