Comparative study on microstructure of Mongolian pine wood thermally treated in steam condition

Mongolian pine wood was thermally treated at 205°C in atmospheric steam. Microstructure of heat-treated and control samples was investigated by means of light microscopy and scanning electronic microscopy (SEM). The results showed radial cracks between ray parenchyma cells and tracheids in latewood of heat-treated Mongolian pine. Besides, fissures were found between tracheids of heat-treated samples, especially at cell corners. Thermal degradation of cell wall components during heat treatment is considered as the main reason for the cracks and fissures. In light microscopy observation, earlywood tracheids of heat-treated samples were found curved or even cleaved. That is most probably due to the force of microtome knife, while not the direct outcome of heat treatment. No significant alteration of bordered pits or crossfield pits was found after heat treatment.