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 the cell turgor pressure, which stretches the cell wall. The wall's resistance to stretching simultaneously creates wall stress and its counter force, turgor pressure. This wall stress relaxation is caused by a protein expansin, it is done 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.
Discuss the meaning and significance of the term "stress relaxation" in relation to the process of plant cell expansion. Why is stress relaxation crucial for the process of plant growth.