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Nanomechanical characterization of developing wood cell walls at different maturation steps
Olivier Arnould
Last modified: 2009-11-06
Abstract
Karl Bytebier,1 Olivier Arnould,1 Richard Arinero,2 Bruno Clair, 1 Tancr`ede Alm'eras1
1 Laboratoire de M'ecanique et G'enie Civil, Universit'e de Montpellier 2/CNRS UMR5508
cc 048 - Place Eug`ene Bataillon, 34095 Montpellier, France
2 Institut d'Electronique du Sud, Universit'e de Montpellier 2/CNRS UMR5214
cc 082 - Place Eug`ene Bataillon, 34095 Montpellier, France
The mechanical properties of wood originate in those of its secondary cell walls. Secondary walls are formed during cell differentiation by addition of constitutive material (cellulose, hemicellulose and lignin) extruded by the plasma membrane and progressively incorporated to the wall. The mechanical properties of the wall depend on the amount of constitutive polymers, their spatial organisation, and also on the way they are bound to each other during cell development. To date, very few is known about how the mechanical properties of a wall layer progressively change during the early stages of its formation. A better knowledge of the timing of the wall stiffening may be useful to understand its assembly process. More specifically, it is necessary for understanding and modelling the apparition of maturation stress in wood [Yamamoto et al., 2002; Alm'eras et al., 2005; Goswami et al., 2008], because wall stiffness determines the amount of stress generated by an impeded dimensional changes of its constituents.
In this context, our goal is to measure mechanical properties within the different layers and their evolution during wall formation, in order to know, for example, if the stiffening of the secondary layers occurs immediately after their deposition, if there is a time lag between wall formation and stiffening, or if the whole wall stiffens simultaneously at the end of its formation. In an other way, what is the gradient in mechanical properties within the cell wall during its formation, and how does this gradient change during the time course of the maturation process? This can be assessed by mapping the mechanical properties of cell walls taken along a differentiation sequence, from the cambium to mature wood. The most used characterization techniques at the cell wall scale are based on instrumented nanoindentation [Gindl et al., 2002; Tze et al., 2007]. Unfortunately, the spatial resolution of these methods is not enough to measure neither gradient properties in the cell wall nor mechanical properties of a thin layer. In our case, we used a specific mode of an atomic force microscope, called force modulation [Clair et al., 2003; Rabe, 2006], in contact mode. A mathematical processing [Arinero et al., 2007] associated with the use of measurement on reference materials and modelling of the AFM cantilever vibration allow us to draw semi-quantitative images of the contact average elastic modulus and damping of secondary cell wall layers at different maturation steps.
Alm'eras T., Gril J., Yamamoto H. (2005) Modeling the tangential released maturation strains in wood in relation with fiber microstructure and maturation kinetics. Holzforschung, vol. 59, pp. 347-353.
Arinero, R., L'ev`eque, G., Girard, P. et Ferrandis, J.Y. (2007), Image processing for resonance frequency mapping in atomic force microscopy. Review of Scientifc Instruments, 78, 6p.
Clair, B., Arinero, R., L'ev`eque, G., Ramonda, M. et Thibaut, B. (2003), Imaging the mechanical properties of wood cell wall layers by atomic force modulation microscopy. IAWA Journal, 24, pp. 223-230.
Gindl W., Gupta H.S., Gr"unwald C. (2002), Lignification of spruce tracheid secondary cell walls related to longitudinal hardness and modulus of elasticity using nano-indentation. Canadian Journal of Botany, vol. 80, pp. 1029-1033.
Goswami L., Dunlop J.W.C., Jungnikl K., Eder M., Gierlinger N., Coutand C., Jeronimidis G. Fratzl, P. et Burgert, I. (2008), Stress generation in the tension wood of poplar is based on the lateral swelling power of the G-layer. Plant Journal, vol. 56, pp. 531-538.
Rabe U. (2006), Atomic force acoustic microscopy. In: Applied Scanning Probe Methods II: Scanning Probe Microscopy Techniques, Bhushan, B. and Fuchs, H. (Eds), Springer-Verlag, Berlin, 36-90.
Tze W.T.Y., Wang S., Rials T.G., Pharr G.M. et Kelley S.S. (2007), Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements. Composites: Part A, vol. 38, pp. 945-953.
Yamamoto H., Kojima Y., Okuyama T., Abasolo W.P. et Gril J. (2002), Origin of the biomechanical properties of wood related to the fine structure of the multi-layered cell wall. Transactions of the ASME, vol. 124, pp. 432-440.
1 Laboratoire de M'ecanique et G'enie Civil, Universit'e de Montpellier 2/CNRS UMR5508
cc 048 - Place Eug`ene Bataillon, 34095 Montpellier, France
2 Institut d'Electronique du Sud, Universit'e de Montpellier 2/CNRS UMR5214
cc 082 - Place Eug`ene Bataillon, 34095 Montpellier, France
The mechanical properties of wood originate in those of its secondary cell walls. Secondary walls are formed during cell differentiation by addition of constitutive material (cellulose, hemicellulose and lignin) extruded by the plasma membrane and progressively incorporated to the wall. The mechanical properties of the wall depend on the amount of constitutive polymers, their spatial organisation, and also on the way they are bound to each other during cell development. To date, very few is known about how the mechanical properties of a wall layer progressively change during the early stages of its formation. A better knowledge of the timing of the wall stiffening may be useful to understand its assembly process. More specifically, it is necessary for understanding and modelling the apparition of maturation stress in wood [Yamamoto et al., 2002; Alm'eras et al., 2005; Goswami et al., 2008], because wall stiffness determines the amount of stress generated by an impeded dimensional changes of its constituents.
In this context, our goal is to measure mechanical properties within the different layers and their evolution during wall formation, in order to know, for example, if the stiffening of the secondary layers occurs immediately after their deposition, if there is a time lag between wall formation and stiffening, or if the whole wall stiffens simultaneously at the end of its formation. In an other way, what is the gradient in mechanical properties within the cell wall during its formation, and how does this gradient change during the time course of the maturation process? This can be assessed by mapping the mechanical properties of cell walls taken along a differentiation sequence, from the cambium to mature wood. The most used characterization techniques at the cell wall scale are based on instrumented nanoindentation [Gindl et al., 2002; Tze et al., 2007]. Unfortunately, the spatial resolution of these methods is not enough to measure neither gradient properties in the cell wall nor mechanical properties of a thin layer. In our case, we used a specific mode of an atomic force microscope, called force modulation [Clair et al., 2003; Rabe, 2006], in contact mode. A mathematical processing [Arinero et al., 2007] associated with the use of measurement on reference materials and modelling of the AFM cantilever vibration allow us to draw semi-quantitative images of the contact average elastic modulus and damping of secondary cell wall layers at different maturation steps.
Alm'eras T., Gril J., Yamamoto H. (2005) Modeling the tangential released maturation strains in wood in relation with fiber microstructure and maturation kinetics. Holzforschung, vol. 59, pp. 347-353.
Arinero, R., L'ev`eque, G., Girard, P. et Ferrandis, J.Y. (2007), Image processing for resonance frequency mapping in atomic force microscopy. Review of Scientifc Instruments, 78, 6p.
Clair, B., Arinero, R., L'ev`eque, G., Ramonda, M. et Thibaut, B. (2003), Imaging the mechanical properties of wood cell wall layers by atomic force modulation microscopy. IAWA Journal, 24, pp. 223-230.
Gindl W., Gupta H.S., Gr"unwald C. (2002), Lignification of spruce tracheid secondary cell walls related to longitudinal hardness and modulus of elasticity using nano-indentation. Canadian Journal of Botany, vol. 80, pp. 1029-1033.
Goswami L., Dunlop J.W.C., Jungnikl K., Eder M., Gierlinger N., Coutand C., Jeronimidis G. Fratzl, P. et Burgert, I. (2008), Stress generation in the tension wood of poplar is based on the lateral swelling power of the G-layer. Plant Journal, vol. 56, pp. 531-538.
Rabe U. (2006), Atomic force acoustic microscopy. In: Applied Scanning Probe Methods II: Scanning Probe Microscopy Techniques, Bhushan, B. and Fuchs, H. (Eds), Springer-Verlag, Berlin, 36-90.
Tze W.T.Y., Wang S., Rials T.G., Pharr G.M. et Kelley S.S. (2007), Nanoindentation of wood cell walls: Continuous stiffness and hardness measurements. Composites: Part A, vol. 38, pp. 945-953.
Yamamoto H., Kojima Y., Okuyama T., Abasolo W.P. et Gril J. (2002), Origin of the biomechanical properties of wood related to the fine structure of the multi-layered cell wall. Transactions of the ASME, vol. 124, pp. 432-440.