Morphological aspects of wood degradation

Many species of white rot fungi can selectively degrade lignin from coniferous and deciduous wood without extensive loss of cellulose. The patterns of cell wall degradation are distinct from the decay patterns caused by other white rot fungi that simultaneously degrade all cell wall components, as well as from other types of decay. Advanced stages of decayed wood that is lignin free can easily be identified in the field and laboratory using various histological reagents. These reagents result in color changes that aid in macroscopic observations and identification of delignified wood. This chapter discusses the morphological aspects of wood degradation. Micromorphological and ultrastructural techniques are needed for precise determinations and to identify the sequential changes that occur during the process of lignin degradation within woody cell walls. The spatial relationships between fungal enzymes and sites of cell wall attack can be elucidated using these techniques. The chapter discusses the quantitative data on lignin distribution in different morphological regions of the cell wall that can be obtained by coupling scanning electron microscopy with energy-dispersive X-ray analysis.