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Nanoindentation-based Methods for Studying the Mechanical Behavior of Living Plant Cells
Plant cell walls are complex and dynamic structures mainly composed of a network of extended polysaccharides providing structural support and protection to the cell. Thickness, rigidity, and extensibility of the cell wall determine the size, shape, morphology, and growth behavior of a plant. In addition, the turgor pressure within each cell changes throughout the life cycle of the plant in response to genetic and environmental changes. The connection between the plant biology and the mechanical response of the cell (e.g., turgor pressure and cell wall viscoelasticity) will provide insight into mechanisms responsible for cell adaptation. In this dissertation, nanoindentation-based methods are used to study the mechanics of the plant cell. In the first section, a new in vivo method is presented to determine turgor pressure within plant cells based upon quasi-static nanoindentation using cyclic tests with variable depth combined with finite element simulations. The method is verified by testing samples (Arabidopsis thaliana) at different environmental conditions including, normal, turgid, and plasmolyzed. The response of the plant cell wall depends upon parameters including the geometry of the cell wall, turgor pressure, radius of the indenter, the viscoelastic properties of the cell wall, and the turgor pressure. These properties are also quantified at various stages of plant development. Next, using a similar combination of experiments and simulations, the failure stress of a plant cell wall is determined. For this purpose is nanoindentation experiments have been carried on Arabidopsis thaliana using spherical tips varying in diameter from 70 nm to 3 µm. Load-displacement profiles obtained from experiments suggest that there is an optimum diameter of tip size which can be used to penetrate the tip through the cell wall. The computational model is used along with the known parameters to study the effect of the tip size on load displacement behavior and stresses. The effect of failure stress is investigated in plasmolyzed, normal and turgid conditions. Finally in the last section of this dissertation the knowledge obtained in the previous sections is used to investigate the potential of injecting molecules inside plant cells. The preliminary results suggest the potential for molecule delivery without damaging the cell. However, much more work is needed to enhance the yield to a sufficient level for studies of single-cell plant biology.
Plant biology|Engineering|Biomechanics|Materials science
Forouzesh, Elham, "Nanoindentation-based Methods for Studying the Mechanical Behavior of Living Plant Cells" (2012). ETD collection for University of Nebraska - Lincoln. AAI3505127.