Transverse swelling behavior of hinoki (Chamaecyparis obtusa) revealed by the replica method

Transverse swelling and its anisotropy in hinoki (Chamaecyparis obtusa) in several kinds of organic liquids and in water were investigated by means th e replica method. There was more cross-sectional swelling of cell walls and cell wall thickness in earlywood than in latewood. Marked swelling toward cell lumens was observed in wood swollen in liquids that had higher swellin g potentials than water. This suggests that the swelling of cell walls in t hese liquids is much greater than the external swelling. Feret's diameters of the cell lumens were reduced by swelling in all the observed cases excep t in the tangential direction of earlywood, suggesting that cell walls swel l to a much less extent in width than in thickness. Deformation of cell sha pes caused by the tensile force from the latewood were observed in the earl ywood and in the transitional region from earlywood to latewood. When swoll en in water, transverse swelling anisotropy caused only by the swelling in cell wall thickness were calculated to be 1.2 for the whole region over an annual ring and 1.4 for the earlywood. These values could not account for t he external swelling anisotropy of 2.1. Considering obvious deformations of cell shapes in the earlywood and in the transitional region, we conclude t hat the interaction between earlywood and latewood is one of the prime fact ors contributing to the transverse swelling anisotropy of coniferous wood.