Cell Growth and the Structure and Mechanical Properties of the Wall in Internodal Cells ofNitella opaca: II. MECHANICAL PROPERTIES OF THE WALLS

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Abstract
SUMMARY The internodal cells of Nitella opaca L. have been used in an attempt to assess the part which mechanical properties of the wall may play in the control of cell growth. It is shown that the wall is mechanically anisotropic in both its plastic and elastic properties, and evidence is presented which indicates that this arises from its anisotropy of structure. The degree of anisotropy is greater in cells with a high growth-rate than in those with a low growth-rate. Evidence is presented that this variation in properties with growth-rate is due wholly, or in part, to changes in the orientation of the crystalline component, in the relative proportion of wall constituents, and in the condition of active groups of the wall components. The findings are in harmony with the theory that extension growth of the cell wall is due to ‘creep’, i.e. disturbances of the molecular forces within the wall leading to a slow plastic yielding to turgor pressure.