Abstract: Meticulous chemical analysis of decaying xylem and linking it to corresponding anatomical modification at the cellular level can improve our understanding of the decay process. The aim of this study was to monitor the histological, chemical, photochemical, and progression of wood degradation by two white-rot fungi at different intervals. Oriental beech wood (Fagus orientalis) blocks were exposed to Pleurotus ostreatus and Trametes versicolor to investigate the degradation capabilities of these two fungi. Light microscopy was used to study the decay patterns in wood. Decayed wood samples were also analyzed to determine lignin, cellulose and sugar contents and also evaluated at two week intervals by FT-IR spectroscopy to study chemical alterations. According to chemical analyses lignin is the most degraded polymer followed by cellulose and hemicelluloses for both white rot fungi. However, both test fungi tended to consume lignin more than cellulose. FT-IR spectra changes for lignin and carbohydrates in beech wood supported chemical alteration and indicated that both fungi decay wood in a simultaneous pattern.

ABSTRACT The impacts of white-rot fungi on altering wood chemistry have been studied mostly in vitro. However, in vivo approaches may enable better assessment of the nature of interactions between saprotrophic fungi and host tree in nature. Hence, decayed and sound wood samples were collected from a naturally infected tree (Carpinus betulus L.). Fruiting bodies of the white rot fungus Trametes versicolor grown on the same tree were identified using rDNA ITS sequencing. Chemical compositions (cellulose and lignin) of both sound and infected wood were studied. FT-IR spectroscopy was used to collect spectra of decayed and un-decayed wood samples. The results of chemical compositions indicated that T. versicolor reduced cellulose and lignin in similar quantities. Fungal activities in decayed wood causes serious decline in pH content. The amount of alcohol-benzene soluble extractives was severely decreased, while a remarkable increase was found in 1% sodium hydroxide soluble and hot water extractive contents in the decayed wood samples, respectively. FT-IR analyses demonstrated that T. versicolor causes simultaneous white rot in the hornbeam tree in vivo which is in line with in vitro experiments.

As to the importance of permeability in the preservation process of solid woods, the effects of diffusion drying schedule with three different initial moisture contents (MC) on fluid flow in the sapwood and heartwood of paulownia wood (Paulownia fortunei) were studied here. Boards with initial MCs of 113 % (D-1), 75.5 % (D-2) and 53.5 % (D-3) were dried to the final moisture content of 8 ± 2 %. Results showed a significant difference in the specific gas and liquid permeability of paulownia wood dried with these different initial MCs. Although gas permeability of sapwood and heartwood specimens was significantly different, no significant difference was seen in liquid permeability between these two parts. D-2 and D-1 showed the highest specific gas and liquid permeability, respectively. It was therefore concluded that the initial MC has a significant effect on the gas and liquid permeability of paulownia boards dried under diffusion schedule with different MCs. Furthermore, the presence of tyloses plays a more important role in permeability than vessel size and frequency by forming an impermeable barrier, resulting in a significant decrease in gas and liquid permeability in paulownia wood.

En cuanto a la importancia de la permeabilidad en el proceso de preservación de maderas macizas, se estudiaron los efectos del programa de secado de difusión con tres diferentes contenidos de humedad (MC) iniciales en el flujo de fluido en la albura y el duramen de la madera de paulonia (Paulownia fortunei). Los tableros con MC iniciales de 113 % (D-1), 75,5 % (D-2) y 53,5 % (D-3) fueron secados al contenido de humedad final de 8 ± 2 %. Los resultados mostraron una diferencia significativa en la permeabilidad específica del gas y del líquido de madera de paulonia secada con estos diferentes MC iniciales. Aunque la permeabilidad al gas de la albura y duramen fue significativamente diferente, no se observó ninguna diferencia significativa en la permeabilidad a los líquidos entre estas dos partes. D-2 y D-1 mostraron la mayor permeabilidad al gas y a los líquidos, respectivamente. Por tanto, se concluyó que el MC inicial de paulonia tiene un efecto significativo sobre la permeabilidad al gas y al líquido de la madera secada con programas de difusión con diferentes MC. Además, la presencia de tilosis juega un papel más importante en la permeabilidad que el tamaño y la frecuencia de los vasos mediante la formación de una barrera impermeable, lo que resulta en una disminución significativa en la permeabilidad de gas y líquido en madera de paulonia.