Mechanical properties of epidermal cells of whole living roots ofArabidopsis thaliana: An atomic force microscopy study

Abstract

The knowledge of mechanical properties of root cell walls is vital to understand how these properties interact with relevant genetic and physiological processes to bring about growth. Expansion of cell walls is an essential component of growth, and the regulation of cell wall expansion is one of the ways in which the mechanics of growth is controlled, managed and directed. In this study, the inherent surface mechanical properties of living Arabidopsis thaliana whole-root epidermal cells were studied at the nanoscale using the technique of atomic force microscopy (AFM). A novel methodology was successfully developed to adapt AFM to live plant roots. Force-Indentation (F-I) experiments were conducted to investigate the mechanical properties along the length of the root. F-I curves for epidermal cells of roots were also generated by varying turgor pressure. The F-I curves displayed a variety of features due to the heterogeneity of the surface. Hysteresis is observed. Application of conventional models to living biological systems such as cell walls in nanometer regimes tends to increase error margins to a large extent. Hence information from the F-I curves were used in a preliminary semiquantitative analysis to infer material properties and calculate two parameters. The work done in the loading and unloading phases (hysteresis) of the force measurements were determined separately and were expressed in terms of "Index of Plasticity" (η), which characterized the elasticity properties of roots as a viscoelastic response. Scaling approaches were used to find the ratio of hardness to reduced modulus (H/E(*)).

Nanometrology of Biomass for Bioenergy: The Role of Atomic Force Microscopy and Spectroscopy in Plant Cell Characterization

“…The first force measurements with AFM also invoked a nanoindenter, but with an improved lateral resolution down to a few nanometers (Kirby, 2011;Fernandes et al, 2012). More recently, quantitative force-volume mapping (QFM) was adapted to plant cell wall measurements utilizing continuous force curve recording and therefore solving the problem of heterogeneity observation by imaging the topography with the associated E and PI mappings.…”

Matching Patterns of Gene Expression to Mechanical Stiffness at Cell Resolution through Quantitative Tandem Epifluorescence and Nanoindentation

“…Several groups have recently achieved mechanical measurements made at a subcellular resolution in plants (Milani et al, 2011;Peaucelle et al, 2011;Fernandes et al, 2012;Radoti c et al, 2012;RoutierKierzkowska et al, 2012) using scaled-down indentation methods (Geitmann, 2006;Hayot et al, 2012;Milani et al, 2013;Routier-Kierzkowska and Smith, 2013), wherein one quantifies the force needed to push down on a sample to a prescribed depth. These studies have revealed spatiotemporal patterns of stiffness, notably in tissues (Milani et al, 2011;Peaucelle et al, 2011;Fernandes et al, 2012;RoutierKierzkowska et al, 2012).…”

Development of New Methods in Scanning Probe Microscopy for Lignocellulosic Biomass Characterization

“…3), one obtains the local mechanical properties of the sample (e.g., Young modulus E, adhesion forces, stiffness, etc.). 20 Here we carried out force curve measurements and analyzed the results using a commercial analysis software, Bruker Nanoscope (Bruker AXS, Madison, WI). By fitting the approach curves (Fig.…”