Trees can control their shape and resist gravity thanks to their ability to produce wood under tensile stress. This stress is known to be produced during the maturation of wood fibres but the mechanism of its generation remains unclear. This study focuses on the formation of the secondary wall in tension wood produced in artificially tilted poplar saplings. Thickness of secondary wall layer (SL) and gelatinous layer (GL) were measured from cambium to mature wood in several trees sampled at different times after tilting. Measurements on wood fibres produced before tilting show the progressive increase of secondary wall thickness during the growing season. After the tilting date, SL thickness decreased markedly from normal wood to tension wood while the total thickness increased compared to normal wood, with the development of a thick GL. However, even after GL formation, SL thickness continues to increase during the growing season. GL thickening was observed to be faster than SL thickening. The development of the unlignified GL is proposed to be a low cost, efficient strategy for a fast generation of tensile stress in broadleaved trees.

This research investigated the effect of chemical modification with vinyl acetate in combination with different coupling agents (maleic anhydride, 3‐(trimethoxysilyl) propyl methacrylate and glycidyl methacrylate) on chemical structure and physical properties of poplar wood. Samples were impregnated with chemicals using vacuum‐pressure method following by vinyl acetate. Fourier transform infrared analysis results confirmed cell wall chemical modification, that was more obvious for glycidyl methacrylate ones. Dimensional stability of resultant composite enhanced via crosslink formation between modified wood and polymer, which affected by cell wall modification rather than in situ polymerization. In comparison of coupling agents, glycidyl methacrylate mostly improved the physical properties of wood as well as combined modified composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47467.