Abstract
Tension wood is a reaction wood formed in the upper side of leaning stem of angiosperm. Reaction wood causes the stem to bend upwards by its mechanical action. However, the mechanism how tensile stress is generated in tension wood is still unknown. Xyloglucan, which is an important component in the primary wall, was found in G-layer of tension wood. So, tension wood induction was tried in the transgenic poplar expressing a xyloglucanase. Both transgenic and wild plants began to bend upwards soon when they were set horizontally. However, the transgenic plants did not continue to bend upward straightly but twisted. Nevertheless, tension wood was formed in all the plants. The result shows that xyloglucan would play an important role to arise tensile stress, rather than to form tension wood. In addition, the normal gravitropism occurs with differential growth in the elongation region even under the degradation of xyloglucan.
