How cell wall structure, mechanics and extensibility relate to the plant cell growth
How cell wall elasticity, plasticity, and time-dependent extension (creep) relate to one another, to cell wall structure and to plant cell growth remain unsettled topics. I will describe recent work that uses atomic force microscopy, enzymes and comparisons of four biomechanical assays to examine these issues. Driselase, a potent cocktail of wall-degrading enzymes, removed cellulose microfibrils in superficial lamellae sequentially, layer-by-layer, and softened the wall (reduced its mechanical stiffness), yet did not induce wall loosening (creep). In contrast Cel12A, a bifunctional xyloglucanase/cellulase, induced creep with only subtle changes in wall appearance. Both Driselase and Cel12A increased the tensile compliances whereas pectate lyase greatly increased indentation compliance without changing tensile compliances. The actions of α-expansins was much more subtle. We conclude that cell wall creep and tensile stiffness depend primarily on cross-lamellate networks of cellulose microfibrils whereas pectins influence indentation mechanics. This information is crucial for molecular models that define how wall mechanics and growth depend on primary cell wall structure.
Cosgrove DJ: 2018. Diffuse Growth of Plant Cell Walls. Plant Physiology 176:16-27.
Zhang T, Vavylonis D, Durachko DM, Cosgrove DJ: 2017. Nanoscale movements of cellulose microfibrils in primary cell walls. Nat Plants 3:17056.
Growing cell walls have complex biomechanical properties. Based on four different assays we conclude that wall creep and tensile stiffness depend on cross-lamellate networks of cellulose microfibrils whereas pectins influence indentation mechanics.