Free access
Issue
Ann. For. Sci.
Volume 57, Number 8, December 2000
Page(s) 739 - 746
DOI http://dx.doi.org/10.1051/forest:2000156
DOI: 10.1051/forest:2000156

Ann. For. Sci. 57 (2000) 739-746

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

Masato Yoshida - Tomonobu Okuda - Takashi Okuyama

Laboratory of Bio-Material Physics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan

(Received 19 July 1999; accepted 28 February 2000)

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$^\circ$ (vertical) to 20$^\circ$. At inclinations over 20$^\circ$, 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.


Keywords: artificial inclination / tensile growth stress / tension wood / Prunus spachiana Kitamura f. ascendens Kitamura / Liriodendron tulipifera Linn

Résumé:

Bois de tension et contrainte de croissance induits par inclinaison artificielle chez Liriodendron tulipifera Linn. et Prunus spachiana Kitamura f. ascendens Kitamura. La relation entre la contrainte de croissance et le niveau d'inclinaison artificielle a été étudiée sur des pousses de deux espèces angiospermes. La contrainte de croissance de traction générée par Prunus spachiana, qui produit des fibres gélatineuses, est plus forte que celle de Liriodendron tulipifera, qui n'en produit pas. Dans les deux espèces, une augmentation de l'inclinaison de 0 à 20$^\circ$ par rapport à la verticale, produit proportionnellement une augmentation de la contrainte de traction générée sur la face supérieure de la tige inclinée et une décroissance de l'angle des microfibrilles cellulosiques. Des inclinaisons supérieures à 20$^\circ$ ne produisent pas de variation supplémentaire, ni de la contrainte ni de l'angle des microfibrilles. La largeur du cerne en cours de formation augmente linéairement avec l'angle d'inclinaison, toutefois l'excentricité de la croissance n'est pas un facteur contribuant de manière dominante au moment de flexion induisant le retour à la position verticale normale. Cet article révèle le caractère borné de la contrainte de croissance, qui peut augmenter jusqu'à un certain point mais ensuite ne dépasse pas cette limite.


Mots clé : inclinaison artificielle / contrainte de croissance / bois de tension / Prunus spachiana Kitamura f. ascendens Kitamura / Liriodendron tulipifera Linn

Correspondence and reprints: Masato Yoshida
Tel. (81) 52 789 4153; Fax. (81) 52 789 4150; e-mail: yoshida@agr.nagoya-u.ac.jp

Copyright INRA, EDP Sciences

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