Microspectroscopy as applied to the study of wood molecular structure

Abstract

Microspectroscopy gives access to spatially resolved information on the molecular structure and chemical composition of a material. For a highly heterogeneous and anisotropic material like wood, such information is essential when assessing structure/property relationships such as moisture-induced dimensional changes, decay resistance or mechanical properties. It is, however, important to choose the right technique for the purpose at hand and to apply it in a suitable way if any new insights are to be gained. This review presents and compares three different microspectroscopic techniques: infrared, Raman and ultraviolet. Issues such as sample preparation, spatial resolution, data acquisition and extraction of knowledge from the spectral data are discussed. Additionally, an overview of applications in wood science is given for each method. Lastly, current trends and challenges within microspectroscopy of wood are discussed.

Vibrational microspectroscopy enables chemical characterization of single pollen grains as well as comparative analysis of plant species based on pollen ultrastructure

“…Spectral signatures of single pollen grains show strong Mie scattering due to their nearly perfect spherical shape (Lukacs et al 2015). In comparison, nearly perfect absorbance spectra have been obtained, when plant materials have been probed by FTIR microspectroscopy as thin sections (Fackler and Thygesen 2013;Yu 2011). Mie scattering signatures are difficult to remove by spectral pre-processing methods.…”

“…Regarding that plant cells are on average some of the largest eukaryotic cells, in general both techniques have sufficient spatial resolution for the analysis of plant cells and tissues. FTIR and Raman have been applied extensively on various plant structures, such as cell walls, seeds, and leaves, for research on plant physiology, developmental biology, genetics and ecology (Gorzsas et al 2011;Barron et al 2005;Dokken et al 2005;Chen et al 2013;Yu 2011;Gierlinger and Schwanninger 2006;Chylińska et al 2014;Agarwal 2006;Fackler and Thygesen 2013;Gierlinger et al 2012). …”

Bacterial and abiotic decay in waterlogged archaeological Picea abies (L.) Karst studied by confocal Raman imaging and ATR-FTIR spectroscopy

“…Spatially resolved chemical information at the molecular level is needed to gain in-depth insights into the decay mechanisms and residual cell wall structure. Chemical imaging methods are well suited for studying individual wood cell wall layers in situ (Fackler and Thygesen 2013).…”

Annual Variations in Norway Spruce Xylem Studied Using Infrared Micro-spectroscopy

“…The difference in cell wall chemistry between earlywood and latewood implies that the amounts of earlywood and latewood present within each ring may give rise to confounding effects rather than climate signals only in studies where the chemical composition of whole tree rings were analyzed. Therefore, microspectroscopy appears to be a good alternative in studies where the aim is to clarify the effects of temperature and precipitation on xylem cell wall composition, as these techniques offer the spatial resolution required [24]. This approach seems not to have been attempted until recently [25].…”