Protocol for mapping the spatial variability in cell wall mechanical bending behavior in living leaf pavement cells

Abstract

An integrated, experimental-computational approach is presented to analyze the variation of elastic bending behavior in the primary cell wall of living Arabidopsis thaliana pavement cells and to measure turgor pressure in the cells quantitatively under different osmotic conditions. Mechanical properties, size and geometry of cells and internal turgor pressure greatly influence their morphogenesis. Computational models of plant morphogenesis require values for wall elastic modulus and turgor pressure but very few experiments were designed to validate the results using measurements that deform the entire thickness of the cell wall. Because new wall material is deposited from inside the cell, full-thickness deformations are needed to quantify relevant changes associated with cell development. The approach here uses laser scanning confocal microscopy to measure the three-dimensional geometry of a single pavement cell, and indentation experiments equipped with high magnification objective lens to probe the local mechanical responses across the same cell wall. These experimental results are matched iteratively using a finite element model of the experiment to determine the local mechanical properties, turgor pressure, and cell height. The resulting modulus distribution along the periclinal wall is shown to be nonuniform. These results are consistent with the characteristics of plant cell walls which have a heterogeneous organization. This research and the resulting model will provide a reference for future work associated with the heterogeneity and anisotropy of mechanical properties of plant cell walls in order to understand morphogenesis of the primary cell walls during growth and to predict quantitatively the magnitudes/directions of cell wall forces. One sentence summaryThe distribution of elastic modulus of the periclinal cell walls of living Arabidopsis epidermis is nonuniform as measured by bending the entire thickness of the wall. HighlightsO_LIExperimental characterization of the spatial distribution of elastic bending behavior across the periclinal wall C_LIO_LIQuantification of the turgor pressure of the living plant epidermal cells validated with osmotic treatments C_LIO_LIQuantification of the effect of cell geometry on the measured mechanical response C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=176 SRC="FIGDIR/small/432478v1_ufig1.gif" ALT="Figure 1"> View larger version (117K): org.highwire.dtl.DTLVardef@46fcfcorg.highwire.dtl.DTLVardef@8b0ab0org.highwire.dtl.DTLVardef@6aad31org.highwire.dtl.DTLVardef@1909d6a_HPS_FORMAT_FIGEXP M_FIG C_FIG