Effects of cell wall ultrastructure on the transverseshrinkage anisotropy of Scots pine wood

A hypothesis for explaining the differential anisotropicshrinkage behavior of wood has been proposed,and it was based on the differences in the cell wall ultrastructure.The starting point of the consideration is thatwood shrinkage is governed by its chemical composition,ultrastructure, and gross anatomy. It is also well knownthat the transverse shrinkage anisotropy of earlywood(EW) is more pronounced than that of the latewood (LW).In the paper, the cell wall ultrastructure and shrinkageanisotropy has been related to each other, and to thispurpose, a set of crystallographic texture descriptorswas applied. The descriptors are based on X-ray diffraction(XRD) experiments conducted on matched EW samplesfrom different growth rings of Scots pine. The rangeof the microfibril angle (MFA) was identified. The ratio ofthe maxima of inverse pole figures (IPFs) of both the tangential(T) and radial (R) directions was determined. Theratios quantify the inhomogeneity of the spatial arrangementof the ordered areas. The results of the study clearlyindicate that the transverse shrinkage of wood is governedmostly by a specific ultrastructural organization of moderatelyorganized cell wall compounds.