Department of Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, UK.
Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany.
Int J Mol Sci. 2022 May 18;23(10):5651. doi: 10.3390/ijms23105651.
Cell growth in plants occurs due to relaxation of the cell wall in response to mechanical forces generated by turgor pressure. Growth can be anisotropic, with the principal direction of growth often correlating with the direction of lower stiffness of the cell wall. However, extensometer experiments on onion epidermal peels have shown that the tissue is stiffer in the principal direction of growth. Here, we used a combination of microextensometer experiments on epidermal onion peels and finite element method (FEM) modeling to investigate how cell geometry and cellular patterning affects mechanical measurements made at the tissue level. Simulations with isotropic cell-wall material parameters showed that the orientation of elongated cells influences tissue apparent stiffness, with the tissue appearing much softer in the transverse versus the longitudinal directions. Our simulations suggest that although extensometer experiments show that the onion tissue is stiffer when stretched in the longitudinal direction, the effect of cellular geometry means that the wall is in fact softer in this direction, matching the primary growth direction of the cells.
植物细胞的生长是由于细胞壁在膨压产生的机械力作用下松弛所致。生长可以是各向异性的，生长的主要方向通常与细胞壁较低刚度的方向相关。然而，洋葱表皮薄片的应变计实验表明，在生长的主要方向上组织更硬。在这里，我们使用表皮洋葱皮的微应变计实验和有限元方法 (FEM) 建模的组合来研究细胞几何形状和细胞模式如何影响组织水平的机械测量。具有各向同性细胞壁材料参数的模拟表明，伸长细胞的取向会影响组织表观刚度，组织在横向方向上比纵向方向软得多。我们的模拟表明，尽管应变计实验表明，当洋葱组织在纵向拉伸时，组织更硬，但细胞几何形状的影响意味着在这个方向上壁实际上更软，与细胞的主要生长方向相匹配。
