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Visualization of inorganic element distribution in preservative treated wood by SEM-EDXA
2001 - IRG/WP 01-40208
SEM-EDXA was found to be an effective way of visualizing inorganic element distribution in wood as it was possible to examine some inorganic elements at the same time and map the concentration differences in color. Japanese cedar sapwoods were impregnated by vacuum treatment with CuAz or by pressure treatment with CCA preservatives and then distribution of Cu, Cr and As elements in wood were examined by SEM-EDXA. For sapwood treated by CuAz, Cu element was more distributed in latewood tracheids near growth ring boundary, axial parenchyma cells (resin cells) and ray parenchyma cells. Sapwood treated by CCA seemed to have the same distribution of Cu as sapwood treated by CuAz. In resin cells, a lot of crystalline deposits were fringed with CuAz and CCA preservatives. This may indicate predominant interactions between preservatives and chemical constituents of the parenchyma cells.
H Matsunaga, R Matsumura, K Oda


UV-microspectrophotometry of lignin and accessory compounds in wood cell walls of conifers
1999 - IRG/WP 99-20171
The distribution of lignin in the cell wall of conifer tracheids was determined by UV-VIS microspectro-photometer. Wood sections of one micron thickness were measured between the wavelength 240 and 700 nm. Spectral analyses revealed that the conifer lignin associated with the tracheid secondary wall and middle lamella is composed of guiacylpropane units which exhibit a characteristic UV absorption maximum at 280 nm. Therefore, in addition, ultrathin sections were exclusively scanned with this characteristic wavelength. Four examples of application are presented: (1) l the lignin contents of the different cell wall regions of fresh spruce wood, (2) the UV-characterization of highly lignified S2-layers in compression wood, (3) a specific pattern of lignin distribution and its derivatives during degradation by white-rot fungi and (4) the detection of accessory compounds (e.g. podocarpic acid) in the lumen and the cell walls of Podocarpaceae species. Finally, the prospects for actual research concerning detection of accessory compounds from hardwoods are given.
G Kleist, G Koch, J Bauch


Hydrolysis of bordered pits during colonization of conifers by brown-rot fungi
1995 - IRG/WP 95-10103
Brown-rot decay results in rapid reduction in degree of polymerization (DP) of holocellulose with concomitant strength loss (MOR) without removing lignin. Development of new methods of wood protection will require focusing on early events in the sequence of depolymerization. Bordered pit membranes (sapwood) represent a readily available source of non-lignified carbohydrate, ie. pectin and cellulose. Commercial pectinases (Pectinol) and Trichoderma sp. have been shown to degrade pit membranes and increase penetration of preservatives. Brown-rot fungi have previouely been shown to produce oxalic acid (OA) during the decay process. Plant pathogens have been shown to degrade pectin by the synergistic action of OA and polygalacturonase (PG). The OA solubilizes the pectin by chelating the Ca++ and the PG hydrolyses the a-1,4 linkages. We have demonstrated the ability of Postia placenta, Gloeophyllum trabeum and Serpula incrassata to use pectin as a sole carbon sourse and to produce OA and PG on both liquid media and wood. Aspergillus niger and Trichoderma sp. also produce PG on wood but no OA or weight loss. The optimal pH of brown-rot polygalacturonase activity is circa 4.0. As the pH of the wood drope below pH 4, due to acid production during decay, there is a progressive decrease in PG activity and the possibility of acid catalyzed hydrolysis of pit membranes is suggested by increased permeability. We hypothesize that pectin utilization is an essential step during incipient brown-rot decay which helps to initiate fungal metabolism and promote the spread of fungal hyphae between tracheids.
F Green III, J L Tschernitz, T A Kuster, T L Highley


Penetration and absorption of water-borne preservatives in conifers from the Western United States: A preliminary report
1988 - IRG/WP 3475
The treatment of most softwoods from the western United States with waterborne chemicals poses a major challenge. Although many of these species are commercially treated with waterbornes, there is considerable debate about their treatability. At present, there is little or no information on the treatability of western wood species with waterborne chemicals. The lack of accurate treatability information related to current practices makes it difficult to improve treatment processes. To develop this information, the heartwood and sapwood of three western wood species were treated using five chemical formulations. Included in these tests were oxide and salt formulations of chromated copper arsenate as well as chromated copper borate. Retentions were measured by gross absorption while penetration was measured using chrome azurol S for copper, cucurmin/salicylic acid for boron, and ammonium molybdate/O-anisidine/stannous chloride for arsenic. The results are discussed in relation to future research directions.
S Kumar, J J Morrell