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Quantitative Assessment of Cytomechanical Parameters in Plants - a Challenge for Micromanipulation.  A. Geitmann, Institut de recherche en biologie végétale, Département de sciences biologiques, Université de Montréal, Montréal, Québec, Canada.

   The mechanical behavior of organisms and organs is determined by the physical properties of their building blocks, the cells and their components. Cells act as mechanical structures whose morphogenesis is largely determined by the physical properties of its components. Cells are able to resist external physical forces such as gravity and to exert forces by way of growth processes. They are also influenced by external physical forces which play a fundamental role in the regulation of cell functions, including gene induction, protein synthesis, cell growth, and death. To appreciate and eventually model the mechanical aspect of cellular architecture and to understand how cells are able to perceive and to react to applied mechanical forces, we need to investigate and quantify their physical properties.

   The principal concept of quantitative mechano-physical studies consists in the application of calibrated loads or deformations and the subsequent quantification of the object's response. Assessing physical properties at the cellular and subcellular level implies a technical challenge, however, since experimental devices in the appropriate dimension - often making use of micromanipulation - have to be developed.

   All eukaryotic cells share at least two structural building elements that determine cellular morphology: the cytoskeleton and the plasma membrane. In plants, fungi and watermolds two additional features contribute to cellular structure and mechanical behavior: the cell wall and the turgor pressure. In this presentation, an overview will be given over the various experimental approaches that have been developed to assess the physical properties and the mechanical behavior of plant and fungal cells. These include micro- and nano-indentation, atomic force microscopy, instron techniques and tonometer approaches. Finally, devices will be presented that are used to quantify dynamic cellular activities and the generation of forces at cellular and subcellular level.

(Supported by NSERC, FCI, FQRNT, HFSP.)