Reverse-engineering plant cell mechanical properties

Unlike animal systems, plant cell mechanics depend mainly on their stiff extra-cellular matrix - the cell wall - which is stretched due to high hydrostatic turgor pressure (~10 atm) imposed by the cell. Plants evolved strategies to manipulate cell wall properties, controlling organ growth and movement. Measuring the micro-scale mechanical properties of individual plant cells is challenging. Indentation methods are used for the measurement but sensitivity of indenter size and geometry, hinder the separation of the cell wall elasticity and pressure. We developed a novel method to reverse engineer the cellular mechanical properties using osmotic treatments and Finite Element Method(FEM) simulations of pressurized cells. Osmotic experiments reveal the turgor pressure which can be used as an input for mechanical modeling along with the deformed 3D cell wall geometry extracted from experiments. FEM simulations are used to reverse engineer the remaining mechanical properties like Young’s modulus of the cell wall(E) and boundary conditions on the cells. Applying this method to the epidermis of Arabidopsis thaliana early leaf, our results unveil tissue-level stretching, the cellular distribution of E, and the significant influence of surrounding cells on individual cell’s expansion.