Figure 10. Snip-and-fill mechanism for cell wall growth.

Highly schematic model for plant cell wall growth along one axis. (A) Turgor pressure is counterbalanced by load-bearing components in the wall, indicated by stretched springs with cross-links. Loosening of the wall occurs by breaking of covalent or non-covalent bonds. (B) Wall stretches as the load is shifted to the remaining wall components. (C) Space created by expansion allows new cross-links to be inserted, seeding the synthesis or insertion of additional load-bearing components. (D) Following insertion of new material, the original properties of the wall have been restored. The net effect is an increase in the resting length of the wall. Because the insertion of new material in this example is limited by the space created through expansion, residual stresses do not accumulate.