Computer analysis of cell walls
Layers of intertwined fibers make up the plant cell walls. Different types of fibers respond to strain differently. Cellulose microfibrils, for example, can stretch or bend, changing their length from end to end, and can also slide over each other, reorient relative directions, and cluster with neighboring microfibrils. Zhang et al. has developed a computational model based on onion skin epidermis observations that describes how these complex changes in space govern cell wall mechanics. The results provide information on how to design multifunctional fibrous materials.
Science, this issue p. 706
Plants have developed complex cell walls based on nanofibrils to respond to various biological and physical constraints. How strength and extensibility emerges from the mesoscale nanoscale organization of growing cell walls has not been resolved for a long time. We sought to clarify the mechanical roles of cellulose and matrix polysaccharides by developing a coarse-grained model based on polymer physics that recapitulates aspects of the assembly and tensile mechanics of epidermal cell walls. Simple non-covalent binding interactions in the model generate clustered cellulose networks resembling those of primary cell walls and possessing elasticity, stiffness, and stress-dependent plasticity beyond a yield threshold. Plasticity arises from fibrils-fibrils sliding in aligned cellulosic networks. This physical model provides a quantitative overview of fundamental questions in plant mechanobiology and reveals the design principles of biomaterials that combine rigidity, elasticity and extensibility.