a b s t r a c tThe white-rot fungus, Physisporinus vitreus, degrades the membranes of bordered pits in tracheids and consequently increases the permeability of wood, which is a process that can be used by the wood industry to improve the uptake of wood preservatives and environmentally benign wood modification substances to enhance the use and sustainability of native conifer wood species. To understand and apply this process requires an understanding of how a complex system (fungusewood) interacts under defined conditions. We present a three-dimensional fungal growth model (FGM) of the hyphal growth of P. vitreus in the heartwood of Norway spruce. The model considers hyphae and nutrients as discrete structures and links the microscopic interactions between fungus and wood (e.g. degradation rate and degree of opening of pits) with macroscopic system properties, such penetration depth of the fungus, biomass, and distribution of destroyed pits in early-and latewood.Simulations were compared with experimental data. The growth of P. vitreus is characterized by a stepwise capture of the substrate and the effect of this on wood according to different model parameters is discussed.

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, a method was developed 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 white-rot fungus Physisporinus vitreus using high-resolution X-ray computed tomographic microscopy. In addition to classical destructive wood anatomical methods such as light or laser scanning microscopy, this 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 on macroscopic properties such as wood strength and permeability.

Purpose: Bioincising is a biotechnological process for improving the permeability of refractory wood such as Norway spruce heartwood using the wood-decay fungus Physisporinus vitreus. The degradation of the bordered pit membranes by P. vitreus in its first stage of wood colonization enhances the uptake of preservatives and wood modification substances, whereas the strength of the material is not significantly reduced. Methods:We propose to study bioincising by means of a mathematical model, because many factors affect the growth and effects of P. vitreus in Norway spruce in such a complex way that an evaluation of the optimal incubation conditions (i.e. water activity, temperature or pH) is very expensive or even not possible solely using laboratory experiments.Results: Using a hyphal growth model we demonstrate here for the first time how to optimize bioincising by linking the microscopic growth behavior of P. vitreus with macroscopic system properties of the wood. Moreover, we propose universal measures of wood-decay fungi, i.e., penetration velocity, penetration work and penetration capacity, which may figure as measures for the efficiency of wood colonization. For example, our simulation shows that an increase of the hyphal growth rate (i.e. changing the incubation conditions) from 1 to 2 μm·d -1 results in an increase of the mycelium's growth velocity from 0.8 to 1.75 μm·d -1 and an increase of the penetration capacity from 0.5 to 0.6 10 -3 ·mm 2 ·d -1 using a pit degradation rate of 2 μm·d -1 .Conclusions: Information about the penetration velocity, penetration work and penetration capacity is of significance for both its biotechnological use and the study of the colonization strategy of wood-decay fungi in general.