Cellular protuberance formation in walled cells requires the local deformation of the wall and its polar expansion. In many cells, protuberance elongation proceeds by tip growth, a growth mechanism shared by pollen tubes, root hairs, and fungal hyphae. We established a biomechanical model of tip growth in walled cells using the finite element technique. We aimed to identify the requirements for spatial distribution of mechanical properties in the cell wall that would allow the generation of cellular shapes that agree with experimental observations. We based our structural model on the parameterized description of a tip-growing cell that allows the manipulation of cell size, shape, cell wall thickness, and local mechanical properties. The mechanical load was applied in the form of hydrostatic pressure. We used two validation methods to compare different simulations based on cellular shape and the displacement of surface markers. We compared the resulting optimal distribution of cell mechanical properties with the spatial distribution of biochemical cell wall components in pollen tubes and found remarkable agreement between the gradient in mechanical properties and the distribution of deesterified pectin. Use of the finite element method for the modeling of nonuniform growth events in walled cells opens future perspectives for its application to complex cellular morphogenesis in plants.

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Cellulose-based components constitute the bulk of the current insulation for transformers. Cellulose is an organic polymer material which combines excellent electrical properties and good mechanical performance. As a polymeric material, cellulose is very sensitive to moisture and temperature. These factors can influence the electrical and mechanical performance of a transformer throughout its lifetime. In order to ensure the quality of the product during transformer manufacturing, as well as during transformer life-time services, adequate models for predicting the physical properties of its constituents are needed.The present investigation tackles the mechanical description of pressboard. For this purpose, a three dimensional mechanical model is developed for simulating the in-plane and out-of-plane behavior of the pressboard material.The model is based on an anisotropic viscoelastic-viscoplastic constitutive law, which includes features that are particular for cellulosebased materials, e.g. the peculiar double nature of fibernetwork-based and porous material. The material is orthotropic by nature, i.e. the in-plane mechanical properties markedly differ from the out-of-plane ones. Particular regard is taken when considering the effect of out-of-plane stresses which both cause viscous deformation and permanent compaction. The analyses on the mechanical behavior of pressboard are performed by comparing the experimental data on pressboard and the results of model simulations.