Key message Mechanical acclimation of young poplars ( Populus tremula × Populus alba , INRA 717-1B4) submitted to periodic stem bending is mainly driven by compressive strains. Flexure wood and compressive flexure wood exhibit higher mechanical resilience and lower mechanical damage. Context It is well known that thigmomorphogenesis modulates tree growth and the anatomical structure of wood. However, nothing is known about the mechanical behaviour of the tissues of fresh wood formed under mechanical stimulation. Aims We investigated the elastic and plastic properties of the fresh wood of young poplar trees ( Populus tremula × Populus alba , INRA 717-1B4) submitted to periodic controlled stem bending that mimics the mechanical effect of wind. Methods For a set of trees, we applied symmetrical bending treatments, which led to the formation of “flexure wood”. For another set of trees, asymmetrical bending treatments, including compression (or tension) only, were applied and generated specific wood formation: “compressive flexure wood” and “tensile flexure wood”. We investigated the elastic and plastic properties of these woods at the stem and at the local tissue levels. Results The results revealed that fresh wood formed under compressive treatments is more resistant to damage (damage reduced by 44%) and a higher mechanical resilience (+ 33%), suggesting that this tissue is able to withstand higher mechanical strains than “normal wood”. This improvement could explain the higher mechanical strength of the stem to bending (+ 42%). Conclusion When trees experience repetitive mechanical stimulations, they adjust the plastic plastic behaviour of their wood in a way that improves the mechanical safety. This demonstrates the adaptive benefit of the mechanical acclimation of trees.

中文翻译：

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“弯曲木材”的机械特性：活树中的压应力提高了木材的机械弹性和抗损伤能力

关键信息 受到周期性茎弯曲的年轻杨树（Populus tremula × Populus alba，INRA 717-1B4）的机械驯化主要由压缩应变驱动。弯曲木材和压缩弯曲木材表现出更高的机械弹性和更低的机械损伤。背景众所周知，thigmomorphogenesis 调节树木生长和木材的解剖结构。然而，关于在机械刺激下形成的新鲜木材组织的机械行为一无所知。目的我们研究了杨树幼树（Populus tremula × Populus alba，INRA 717-1B4）的新鲜木材的弹性和塑性特性，这些树受到周期性控制的茎弯曲，模拟风的机械效应。方法对于一组树木，我们应用了对称弯曲处理，这导致了“弯曲木”的形成。对于另一组树木，应用了不对称弯曲处理，仅包括压缩（或拉伸），并生成了特定的木材形态：“压缩弯曲木材”和“拉伸弯曲木材”。我们研究了这些木材在茎和局部组织水平上的弹性和塑性。结果 结果表明，在压缩处理下形成的新鲜木材更能抵抗损坏（损坏降低 44%）和更高的机械弹性（+ 33%），表明这种组织能够承受比“普通木材”更高的机械应变. 这种改进可以解释茎的更高的弯曲机械强度（+ 42%）。结论 当树木经历重复的机械刺激时，他们以提高机械安全性的方式调整木材的塑性行为。这证明了树木机械驯化的适应性优势。