Anatomical, chemical, and physical characteristics of tension wood in two tropical fast-growing species, Falcataria moluccana and Acacia auriculiformis

The anatomical, chemical, and physical characteristics of tension wood were investigated in the commercially important tropical fast-growing plantation species Falcataria moluccana and Acacia auriculiformis. In both cases, pots containing seedlings of the two species were tilted at 50° from a vertical position to promote tension wood formation. During this period, upward bending occurred in the seedlings of both the species. Samples were collected from three different stem positions (lower position, middle position, and upper position). A distinct gelatinous (G-) layer was observed at the lower position in F. moluccana, and lower and middle positions in A. auriculiformis. Compared to normal wood, the anatomical and chemical characteristics, except for the vessel frequency, were significantly different at the lower position in F. moluccana, and at the lower and middle positions in A. auriculiformis, pointing to “typical” tension wood in the inclined stems of both species. Compared to normal wood, the basic density significantly increased at the lower position in F. moluccana, but not in A. auriculiformis. Although a common inclination method was used, the position of the G-layer differed between the two species, suggesting that the degree of response to the inclination stimulus varies among species.