Study of tension wood in the artificially inclined seedlings of Koelreuteria henryi Dummer and its biomechanical function of negative gravitropism

• DOI: 10.1007/s00468-015-1304-2
• Publication Date: 2015-10-06T12:30:34Z
• Authors: Li-Fen Hung; Ching-Chu Tsai; Shiang-Jiuun Chen; Yan-San Huang; Ling-Long Kuo-Huang
• Keywords: Tension (geology); Gravitropism; Vascular cambium; Tracheid

Stem reorientation is critical to tree survival. With anatomical observation and strain measurement, the tension wood formation and biomechanical behavior were studied to gain insights into tree uprighting process. Tension wood plays a role in maintaining the mechanical stability of angiosperm trees. Both biological and physical aspects of tension wood are essential in understanding the mechanism of trunk or branch reorientation. In this study, we worked on both tension wood formation and its biomechanical function in artificially inclined 2-year-old Koelreuteria henryi seedlings. The tension wood formation and reorientation process of the trunk last for about 3 months. With pinning method, we confirmed that at the beginning of inclination the cambial zone including the vascular cambium and the developing normal wood fibers on the upper side of the inclined trunk perceives the onset of mechanical change and starts to produce G-fibers that generate a strong contractile released growth strain (RGS) for gravitropic correction. Stronger contractile RGS and more tension wood were found at the trunk base than at the half-height, suggesting that the trunk base plays a key role in trunk uprighting of K. henryi seedlings. The eccentric cambial growth in the tension wood side increases the efficiency of gravitropic correction and the compressive strains measured in the opposite wood of some inclined seedlings also help the upright movement.