Direct investigation of the structural properties of tension wood cellulose microfibrils using microbeam X-ray fibre diffraction

Single tension-wood fibres from poplar were investigated using a synchrotron radiation X-ray microbeam. The resulting diffraction patterns are highly resolved (smallest d-spacing 0.11 nm). In the gelatinous layer, cellulose microfibrils of high perfection are found in almost ideal parallel alignment. Their cross-section is approximately four-fold greater than that of microfibrils in the S2 layer of the same wood cell. The results are discussed in terms of the influence of encrusting cell wall polymers and cellulose biosynthesis on the structure of wood cellulose microfibrils. In temperature-dependent experiments, the low-temperature thermal expansion coefficients of crystalline cellulose were determined.