Blanc SIMI 9 - Blanc - SIMI 9 - Sciences de l'Ingénierie, Matériaux, Procédés, Energie

Coupled physiological and micro-mechanical approach on maturation stress generation in tension wood – StressInTrees

Toward the understanding of the 'muscles' of trees

Biomechanical design of trees is performed thanks to the ability to generate large mechanical stresses in wood at the stem periphery. This function is necessary for the tree to control the orientation of its axes, and therefore to grow in height, maintain its branches at an optimal angle or achieve adaptive reorientations. The aim of the project is to understanding the mechanism of maturation stress generation in trees.

Coupled physiological and micro-mechanical approach on maturation stress generation in tension wood

A key element of the biomechanical design of trees is their ability to generate large mechanical stresses in wood at the stem periphery. This function is necessary for the tree to control the orientation of its axes, and therefore to grow in height, maintain its branches at an optimal angle or achieve adaptive reorientations. This «maturation stress« appears in wood fibres at the end of the formation of their secondary cell wall, but the underlying biophysical process is still unknown. Understanding the mechanism of maturation stress generation is a question of paramount importance in tree physiology, with important technological outcomes regarding wood processing and biomimetic inspiration in material design.

As this research needs to integrate knowledge from plant biology, chemistry, physics and mechanics, the project will be supported by three complementary partners, with excellent expertises on tree biomechanics, micromechanics, wood diversity, tree physiology and molecular biology. This partnership will be complemented with a large network of French and international laboratories covering extra-competences needed for the project. Two plant models are chosen, poplar will represent the species developing a specific unlignified gelatinous layer (G-layer) like most temperate species and simarouba will represent non-G-layer species like two third of tropical species. Whereas most research has been concentrated on G-layer species, our project is a pioneer in the study of the maturation stress mechanisms in non-G-layer species. The strategy relies on i) the determination of both the structural organisation and the mechanical behaviour of wood constituents along the sequence of cell maturation from the cambium to the mature wood and ii) the identification of associated molecular triggers allowing these changes. The observations performed at different scales (macromolecular constituents, cell-wall layer, macroscopic wood), will feed a micro-biomechanical model that will be developed to test the consistency between hypothetic mechanisms and observations made at each level. The research plan is organised in 5 tasks (Molecular triggers, Cellulose and matrix organisation and behaviour, Cell-wall behaviour, Micro-mechanical modelling, Hypotheses testing) designed to solve this old question that still remains enigmatic.

will be completed soon, after publication

will be completed soon, after publication

1. Clair, B., Alteyrac, J., Gronvold, A., Espejo, J., Chanson, B., Alméras, T. (2013) Patterns of longitudinal and tangential maturation stresses in Eucalyptus nitens plantation trees. Annals of Forest Science, September 2013, Open Access DOI 10.1007/s13595-013-0318-4
2. Chang, SS., Salmén, L., Olsson, A-M., Clair, B (2014) Deposition and organisation of cell wall polymers during maturation of poplar tension wood by FTIR microspectroscopy. Planta. 239(1), 243-254. doi:10.1007/s00425-013-1980-3

A key element of the biomechanical design of trees is their ability to generate large mechanical stresses in wood at the stem periphery. This function is necessary for the tree to control the orientation of its axes, and therefore to grow in height, maintain its branches at an optimal angle or achieve adaptive reorientations. This "maturation stress" appears in wood fibres at the end of the formation of their secondary cell wall, but the underlying biophysical process is still unknown. Understanding the mechanism of maturation stress generation is a question of paramount importance in tree physiology, with important technological outcomes regarding wood processing and also for biomimetic inspiration in material design. As this research needs to integrate knowledge from plant biology, chemistry, physics and mechanics, the project will be supported by three complementary partners, with excellent expertises on tree biomechanics, micromechanics, wood diversity, tree physiology and molecular biology. This partnership will be complemented with a large network of French and international laboratories covering extra-competences needed for the project. Two plant models are chosen, poplar will represent the species developing a specific unlignified gelatinous layer (G-layer) like most temperate species and simarouba will represent non-G-layer species like two third of tropical species. Whereas most researches have been concentrated on G-layer species, our project is a pioneer in the study of the maturation stress mechanisms in non-G-layer species. The strategy relies on i) the determination of both the structural organisation and the mechanical behaviour of wood constituents along the sequence of cell maturation from the cambium to the mature wood and ii) the identification of associated molecular triggers allowing these changes. The observations performed at different scales (macromolecular constituents, cell-wall layer, macroscopic wood), will feed a micro-biomechanical model that will be developed to test the consistency between hypothetic mechanisms and observations made at each level. The research plan is organised in 5 tasks (Molecular triggers, Cellulose and matrix organisation and behaviour, Cell-wall behaviour, Micro-mechanical modelling, Hypotheses testing) designed to solve this old question that still remains enigmatic.

Project coordination

Bruno CLAIR (UMR Ecologie des Forêts de Guyane) – bruno.clair@univ-montp2.fr

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

AGPF-INRA Orléans Amélioration, Génétique et Physiologie Forestières
ECOFOG UMR Ecologie des Forêts de Guyane
LMGC Laboratoire de Mécanique et Génie Civil

Help of the ANR 458,759 euros
Beginning and duration of the scientific project: December 2012 - 48 Months

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