Stem tangential strain on the tension wood side of Fagus crenata saplings

Abstract

The tangential strain on the inner bark surface of Fagus crenata sapling stems was continuously measured using strain gauges. The total strain increased daily, increasing at night and decreasing during the day. When tension wood was induced by artificial inclination, the strain increased more on the upper side than on the lower side; and the increment in the strain at night was larger on the upper side than on the lower. The change in tangential strain on the inner bark surface arose from changes in the water content and the volume of differentiating cells. Differentiating tension wood fibers appear to contain more water and to expand more at night than differentiating normal wood fibers. We can determine whether tension wood is formed from the tangential strain during growth.