**3.Changes in microstructure**

The microstructure of wood will also undergo significant changes after being infected by decay fungi, such as the enlarged porosity in the wood due to the partially or entirely destroyed fibers, which could improve the permeability, decrease the density, and reduce the strength and toughness of wood as well, making it prone to fracture [2]. Some morphology observations are illustrated in **Figure 2** (derived from the authors' results [29]). In **Figure 2**, it can be seen that white rot fungi *T. versicolor* almost colonized in cell lumens at 4 weeks due to the obviously present hyphae in the wood cell lumina, and hyphae presented in large clusters after 8 weeks [29]. It can be suggested that white rot fungi *T. versicolor* grew along lumens of wood cell walls during its colonization then the lignin can as well be decomposed accordingly [8, 17]. In brown rot fungi, a large number of cell walls were deconstructed, revealing fungi were able to grow and reproduce, leading to the destruction of wood cell walls. It was also reported that decay fungi colonized and attacked through parenchyma cells via pits and the wood rays were the primary paths for the spread of mycelium [19].

It can be concluded that there also are microstructure changes within wood during the degradation by fungi with the destruction of the cell wall materials, resulting in the enhancement of the accessibility of wood substrates as well as the improvement of the wood permeability.
