Chapter 15 - Microscope Techniques for Understanding Wood Cell Structure and Biodegradation

Abstract

Light and electron microscopy have contributed significantly to revolutionize our understanding of wood structure and its biodegradation. Light (bright field, optical, fluorescence, ultraviolet) microscopy remains the dominant type of wood analysis allowing for global and detailed information of native cellular structure and chemistry as well as degraded wood. Light and electron microscopy (scanning and transmission) techniques provide complementary information from global through tissue, cell, subcellular, and suborganelle levels with high spatial resolution not available using other approaches. Conventional scanning and transmission electron microscopy (SEM/TEM) and ancillary approaches (FE-SEM, ESEM, Cryo-SEM, Cryo-TEM, SEM-EDX, TEM-EDX, and rapid freezing approaches) have greatly improved our finite understanding of the structure of wood cell walls and polymers and of the different morphological forms of wood decay described from light microscopy. SEM and FE-SEM have allowed for the three-dimensional structure of wood to be explored and the intimate nanostructure of the microfibrils and microfibril aggregates within cell wall layers to be revealed as well as providing new details on the interaction of microbes and their mechanisms of decay. The advent of electron tomography techniques with FE-TEM should provide intimate high-resolution three-dimensional imaging of wood ultrastructure and decay not possible previously. Additional imaging and analysis techniques that have been used to reveal aspects of wood (ultra)structure and chemistry (e.g., FTIR, Raman, XPS, ToF-SIMS, AFM, X-ray microtomography) continue to be developed and applied although the various light and electron microscopy approaches still remain the most widely used and influential. In this chapter an outline will be given on the main microscopy techniques applied for studies on wood (ultra)structure and wood decay with examples and limitations. Emphasis will also be given to sample preparation as this is a fundamental prerequisite for achieving optimal results with all microscopy approaches.