How Cell Geometry and Cellular Patterning Influence Tissue Stiffness

Int J Mol Sci. 2022 May 18;23(10):5651. doi: 10.3390/ijms23105651.

Abstract

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.

Keywords: FEM; MorphoMechanX; MorphoRobotX; biomechanics; cell geometry; cell growth; cellular patterning; finite element method; microextensometer; modeling.

MeSH terms

  • Anisotropy
  • Cell Wall* / physiology
  • Mechanical Phenomena*

Grants and funding

This work was supported by ERA-CAPS V-MORPH project (DFG) to R.S.S. and M.M.; John Innes Foundation funding to N.T.; the Plant Morphodynamics FOR2581 Research Unit support to G.M.; and an Institute Strategic Program Grant from the BBSRC to the John Innes Centre (BB/P013511/1).