Geometrical Details Matter for Mechanical Modeling of Cell Morphogenesis.

Morphogenesis of wavy epidermal pavement cells in plants has fascinated researchers for decades. A mechanical mechanism had been proposed in which the anticlinal cell walls, forming the in-plane cell borders, feature contiguous stiff and soft zones that generate waves upon stretching. We replicated this model as designed and also expanded on it to test its validity for three-dimensional (3D) cell geometry. Our results suggest that both the assumptions going into and the predictions arising from this hypothesis do not stand closer scrutiny and may misguide experimentalists. Unlike what the published data seem to suggest, we observed that only waves of negligible magnitude can be formed by this anticlinal stretch model and that these are virtually eliminated when full 3D geometry of the cell is considered. Further, the model produces cell wall stresses that do not match the experimental evidence.