TENSION WOOD-LIKE REACTION WOOD IN VESSEL-LESS TETRACENTRON SINENSE

摘要

The objective of this study is to clarify the anatomical characteristics and lignin distribution of reaction wood in a vessel-less angiosperm species, Tetracentron sinense Oliv. Sample disks (1 cm in thickness) were collected from three different positions of a Tetracentron sinense tree. Cell morphologies, the microfibril angle (MFA) in the S-2 layer, lignin distribution, and lignin content were measured. There was neither a gelatinous (G-) layer nor an S-3 layer on the upper side of inclined samples. However, the secondary wall of the normal tracheids was only weakly stained by Maule and phloroglucinol-HCl. MFA in the S-2 layer and lignin content decreased on the upper side of inclined samples. This qualifies the reaction wood of Tetracentron as "tension wood-like". The so-called "unusual tracheids", typical for the wood of Tetracentron, showed weaker changes in their anatomical and chemical characteristics in reaction wood than normal tracheids, indicating their special function in water transport. It is hypothesized that vessel-less angiosperms rich in syringyl units in their lignin, produce tension wood-like reaction wood on the upper side of inclined stems or branches, with lower MFA and lignin content in their normal tracheid walls, irrespective of whether a typical G-layer is formed or not.