Wall stress relaxation

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Wall stress relaxation refers to the reduction in tensile stress (force per unit area) in cell walls of plants, fungi and bacteria, as a result of movement or rearrangement of the polymeric network that gives the wall its tensile strength. Wall stress usually comes from cell hydrostatic pressure or turgor pressure, which stretches the cell wall. The wall's resistance to stretching simultaneously creates wall stress and its counter force, turgor pressure. In plant cells, the wall-loosening protein named expansin causes wall stress relaxation by loosening the connections between cellulose microfibrils. The resulting decrease in cell turgor pressure and cell water potential creates the necessary water potential gradient that allows water uptake and expansion of the cell.