Stress-based regulation of multicellular plant growth: a finite element modeling approach applied to planar leaf morphogenesis

How thousands of individual cells control their local growth and collectively generate stable and stereotypical macroscopic shapes is an open question. We address this question in plant morphogenesis, that relies on turgor- induced growth, regulated through rheological properties of the cell wall. In particular, it was proposed that cells may adapt these properties according to the mechanical stress they experience. In this scenario stress would provide a directional cue for the orientation in which cellulose fibres are deposited, leading to the anisotropic reinforcement of the walls.The dynamical behavior of such a system is nontrivial. In this work, we combine theoretical and numerical approaches to predict the emergent behavior of a stress-based regulation of growth. In particular, we show that this mechanism can maintain the typical plant growth modes, and amplify asymmetries. This is required to stabilize prolonged phases of asymmetric growth (stem or leaf growth) and, alternatively to escape a given growth regime and generate different levels of symmetry. Using finite element models of multi-layered tissues, we also provide new insights into the collective behavior of full stress-sensing structures, and nontrivial effects of multi-layered plant mechanics.