Fig. 7

TEM micrographs of pine (a, b) and TEM and Cryo-SEM of birch (c–g) wood degraded by G. trabeum after 8 and 10 weeks respectively. G. trabeum in pine (Fig. 6a, b). At this stage, decay causes weakness between the secondary cell wall layers often resulting in cell wall delamination during sectioning (arrowheads). Very little increase in porosity is noted in the brown rot in pine (c–g). G. trabeum attack of the secondary cell walls of birch, in contrast to the pine decay, shows large openings (black arrows) developing, even in the lignin rich middle lamellae between fibers (d–f, white arrows). At high magnifications (g), individual and well-separated cellulose elementary fibrils (black arrowheads) show electron staining of their surfaces. S2 secondary cell wall, FH fungal hyphae. Bars a–f = 0.5 µm, g = 10 nm