XET activity determination in powdered wood samples as an indicator of tension wood, tested on juvenile Populus x euramericana exposed to severe long-term static bending

Leaning stems of woody plants form reaction wood, in hardwood trees termed tension wood (TW). Typical TW fibers, gelatinous fibers (G-fibers), are characterized by an inner gelatinous cell wall layer (G-layer). Xyloglucan endotransglycosylases (XETs) was proposed as the essential enzyme in cell wall modifications in TW, by making xyloglucan (XG) cross-links between G- and S-2-layers in G-fibers, and thus maintaining their contact. The determination of TW presence in a sample is of great importance for the forest products industry, biofuel production, and tree physiology studies. However, TW is not easy to detect visually. The colorimetric assay for XET activity determination as an indicator of TW presence in a sample was tested on powdered stem segments of juvenile Populus x euramericana trees exposed to severe long-term static bending. In parallel, histochemical and ultrastructural characterization of stem samples of bent and control trees was performed. The tested colorimetric assay for XET activity determination could be suggested as a useful and easily applicable tool for fast screening of powdered wood samples for the presence of TW.