Imaging and Measurement of Nanomechanical Properties within Primary Xylem Cell Walls of Broadleaves

Abstract

A technique of atomic force microscopy (AFM) called PeakForce quantitative nanomechanical mapping (PeakForce QNM) is an efficient tool for the quantitative mechanobiological imaging of fibrillar aggregate, human epidermal cell and woody plant cell wall topography (Sweers et al., 2011; Heu et al., 2012; Ďurkovič et al., 2012; Ďurkovič et al., 2013). Here, we describe a detailed protocol for the measurement of nanomechanical properties of primary xylem cell walls in woody plants, for the determination of reduced Young’s modulus of elasticity (MOE), adhesion, deformation, and energy dissipation (Figure 1). This new technique provides direct control of the maximum loading force and the deformation depth in cell wall samples keeping indentations small, while at the same time eliminating damaging lateral forces in order to preserve both the AFM tip and plant sample. High-resolution and non-destructive imaging shed new quantitative mechanistic insights into the structural biology of woody plant cell walls. This procedure can also be adapted for other biological samples with a varying range of stiffness.