Stiffness transitions in new walls post-cell division differ between Marchantia polymorpha gemmae and Arabidopsis thaliana leaves

Plant morphogenesis is governed by the mechanics of the cell wall–a stiff and thin polymeric box that encloses the cells. The cell wall is a highly dynamic composite material. New cell walls are added during cell division. As the cells continue to grow, the properties of cell walls are modulated to undergo significant changes in shape and size without breakage. Spatial and temporal variations in cell wall mechanical properties have been observed. However, how they<br> relate to cell division remains an outstanding question. Here we combine time-lapse imaging with local mechanical measurements via atomic force microscopy to systematically map the cell wall’s age and growth, with their stiffness. We make use of two systems, <em>M. polymorpha</em> gemmae, and <em>A. thaliana</em> leaves. We first characterise the growth and cell division of <em>M. polymorpha</em> gemmae. We then demonstrate that cell division in <em>M. polymorpha</em> gemmae results in<br> the generation of a temporary stiffer and slower growing new wall. In contrast, this transient phenomenon is absent in <em>A. thaliana</em> leaves. We provide evidence that this different temporal behaviour has a direct impact on the local cell geometry via changes in the junction angle. These results are expected to pave the way for developing more realistic plant morphogenetic models and to advance the study into the impact of cell division on tissue growth.