SUMMARY

Atomic Force Microscopy in force modulation mode has been used to study the elastic properties of the different cell wall layers of holm oak and boco. The method is based on the measurement of the resonance frequency of the microscope lever in contact with the sample. This frequency is related to the reduced Young modulus E*=E / (1-ν) of the material, supposed to be isotropic. "Elastic " images of the cell are obtained, simultaneously with the topographic images, which allows the observation of the mechanical properties of the cells at a nanometric scale. Layers G, S1, S2 and ML are clearly distinguished. By comparison with known materials, an estimation of the absolute modulus is given in the range 5 – 20 GPa, but should be taken with care as the inherent anisotropy of the materials has not be taken into account. Key words: wood, cell wall, mechanical properties, elastic modulus