The plant cell wall is made up of hydrated polymetric material, allowing it to have viscoelastic properties.
Wall stress (measured in force per unit area) is created in response to the plant cell's turgor pressure.
[1] Expansion is the result of "creep", or selective wall loosening, which is driven by turgor pressure.
[3] This enlargement is made possible by the sliding of polymers, increasing the cell wall's surface area.
Previous experiments have confirmed that the cellulose microfibril orientation in the primary cell wall is the key for determining the direction of anisotropic growth and expansion.
[3] Opposed to α-expansins, β-expansins drastically reduce the tensile strength of cell walls.
[3] Not only do β-expansins cause "creep" but it also solubilizes polysaccharides in the middle lamella, aiding the penetration of the pollen tube to the plant's ovary.
Gene knockout experiments were used in discovering that bacterial expansins facilitate the colonization of plant tissue.
[3] Xyloglucan endotransglucosylase/endohydrolases (XTHs) are another class of enzymes that play a role in cell wall loosening.
Most XTHs break and put back together xyloglucans that restrict the movement of adjacent cellulose microfibrils in the cell wall.