Analysis of the correlation between mesocarp biomechanics and its cell turgor pressure: A combined FEM-DEM investigation for irrigation-caused tomato cracking.

Fruit mesocarp cracking caused by improper irrigation during development manifests at the macroscale but is ultimately the result of increasing cell turgor pressure at the microscale. Hence, a cell finite element (FE) model including shape, protoplast turgor pressure, and ripening information and a mesocarp tissue block discrete element (DE) model including the features of cell shape and number, were developed to predict the biomechanical correlation between mesocarp and its cell. The validated cell FE model with an internal turgor pressure of 12.9 kPa could reproduce the experimental force-deformation behavior of a single cell in compression up to 11% deformation with an average relative error of 5.8%. The validated mesocarp tissue block DE model could reproduce the experimental force-deformation behavior of a mesocarp block in compression up to 20% deformation with an average relative error of 9.5%. Sensitivity and regression analysis showed that turgor pressure was the most important factor affecting cell biomechanics, followed by cell shape and wall elastic modulus. Similarly, the apparent elastic modulus of the cells has the most significant effect on the mesocarp tissue biomechanics, followed by the number and shape of cells. Finally, a mathematical model was obtained to quantitatively describe the relationship between the elastic modulus of the mesocarp and its cell turgor pressure. This study contributes to a better understanding of the biomechanical mechanisms of irrigation-caused tomato fruit cracking at the cellular level and the development of strategies to prevent fruit cracking through a combination of gene breeding and irrigation management.