Finite element modelling of the mechanical behaviour of onion epidermis with incorporation of nonlinear properties of cell walls and real tissue geometry

• A computational model of plant tissue that incorporates micro-scale geometrical features was developed.
• The models revealed a significant influence of tissue structure on micromechanical properties.
• The models produced force-strain curves that closely matched the experimental data.

In the field of agricultural sciences, numerical modelling has proven to be a valuable tool in finding solutions to practical and scientific issues. In the present study a computational model of plant tissue that incorporates micro-scale geometrical features was developed to provide qualitative and quantitative predictions of the mechanical properties of onion (Allium cepa) epidermis. The simulations of cellular structure behaviour under various mechanical load conditions were carried out using the finite element method (FEM). The models were validated against experimental data from a tensile test of the real tissue strips. The models showed capabilities of simulating large strains (up to 25%) with nonlinear behaviour and produced force-strain curves that closely matched the experimental data. Also, a new insight into the relationship between microstructure and mechanical behaviour was provided for this type of material. The incorporation of the real microstructure resulted in a qualitative improvement of the mechanical characteristics obtained from FEM models of plant tissues. The ability to directly simulate the impact of changes in turgor pressure was limited due to the semi-three dimensional representation of tissue. The general behaviour of tissue resulting from the changes in turgor was approximated using the semi-solid protoplast that replaced the cells liquid. On the basis of a sensitivity analysis it was concluded that the validity of the results provided by the model is largely dependent on accurate measurements of cell wall thickness.