Microscopic observation of transverse swelling of latewood tracheid: Effect of macroscopic/mesoscopic structure

Abstract

In order to study the transverse swelling/shrinkage of wood, the microscopic swelling behavior of latewood tracheid was observed using confocal laser scanning microscopy and the digital image correlation method. A microcrater structure was created on the surface of the specimen by using the ion sputter etching technique to obtain a pattern-rich digital image for image analysis. Douglas fir specimens were conditioned by two methods of absorption: rapid absorption of moisture from hot steam, and slow absorption of moisture from the water vapor of saturated solutions. Latewood tracheid near the surface of the specimen deformed only in the radial direction when the relative humidity of the surrounding air changed rapidly (rapid absorption of moisture from hot steam or absorption/desorption of moisture during the observation). In addition, the diameter of the lumen decreased upon rapid absorption of moisture, whereas it expanded upon slow absorption of moisture. These results indicate that the microscopic swelling behavior of latewood cells is strongly influenced by the macroscopic/mesoscopic structure, for instance, the cell arrangement or the alternation of latewood and earlywood. © The Japan Wood Research Society 2006.