Tension wood and growth stress induced by artificial inclination in Liriodendron tulipifera Linn. and Prunus spachiana Kitamura f. ascendens Kitamura

Abstract

The relationship between the amount of growth stress and the degree of artificial inclination was investigated in saplings of two angiosperm species. The tensile growth stresses generated in Prunus spachiana, which forms gelatinous fibers, were larger than those in Liriodendron tulipifera, which does not form gelatinous fibers. In both species, the tensile growth stresses generated in the upper side of inclined stems increased and the cellulose microfibrillar angle decreased proportionally as the inclination changed from 0° (vertical) to 20°. At inclinations over 20°, the tensile growth stress and cellulose microfibrillar angle did not change further. The thickness of the current growth layer increased linearly with the angle of inclination, but eccentric growth was not the main factor contributing to the upward bending moment to return the axis to the normal vertical position. This paper reveals that the growth stress generated by inclination is limited. That is, growth stress increases with the inclination angle to a point, but then does not increase further.