Contact-breaking, pore-space patterning and network formation in spongy mesophyll development*

Morphogenesis, or the emergence of spatial structure and heterogeneity during biological development, is driven by cell growth, proliferation, and changes in cell properties, which gives rise to patterns and ultimately function in young tissues. Schizogeny, or the formation of pore space via separation of formerly adherent cells, occurs frequently during plant tissue morphogenesis. While schizogeny is known to pattern pore space in developing roots, here we study more poorly understood schizogeny during the development of the spongy mesophyll tissue of leaves and flowers. We develop a two-dimensional computational model of discrete, deformable particles to mimic the developmental process from confluent mesophyll progenitor cells to porous, network-like mature cells with highly non-spherical shapes. We show that proper development of the spongy mesophyll requires a careful balance of cell-cell adhesion, contact breaking, and the aging of elasticity in the cell wall. We discuss the impact of cell boundary-driven stress on global tissue morphology and anisotropy, as well as extensions to three spatial dimensions.