Viscoelastic properties of plant cell walls—I. Mathematical formulation for stress relaxation with consideration for pre-extension rate

Stress relaxation analysis was used to measure mechanical properties of the cell wall. Although a pre-extension period is needed to give the initial stress or strain to a cell wall specimen in the experiments, studies reported in literature have assumed its length to be zero. Thus, the parameters obtained may not represent characteristic properties of the cell wall, which vary depending upon the pre-extension conditions. A mathematical formulation for stress relaxation with consideration for pre-extension was established by introducing a correction factor K in order to obtain parameters which represent characteristic mechanical properties of the cell wall. The validity of this treatment was examined by comparing the calculated values with experimental data.