Regulation on mechanical properties of spherically cellular fruits under osmotic stress

The texture of fruits is closely related to their mechanical properties (e.g., elastic modulus), which is largely influenced by the osmotic stress. As known to all, the turgor pressure changes under osmotic stress. However, it is unclear how osmotic stress quantitatively changes the turgor pressure and deforms the cells, which further affects the mechanical properties of fruits. In the current study, combining the van't Hoff theory of osmotic pressure with the self-consistent method, we developed a cross-scale theoretical model by considering the osmotic equilibrium, mechanical balance and substance conservation. We found that increasing the external osmotic stress changes the osmotic equilibrium, decreases the turgor pressure, shrinks the cells, enlarges the intercellular space, and softens the fruit tissue. The estimated Young's modulus under osmotic stress agrees with the experimental results.