Effect of Turgor Pressure and Cell Size on the Wall Elasticity of Plant Cells

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Abstract
Direct measurements of the volumetric elastic modulus, ∈, of cells of a higher plant were performed on the epidermal bladder cells of Mesembryanthemum crystallinum using a pressure probe technique. Measurements on giant algal cells (Valonia, Nitellopsis) are given for comparison. Giant celled algae and M. crystallinum bladders have elastic moduli, ∈, which depend strongly on turgor pressure, P, and on cell volume, V. The ∈ values of Mesembryanthemum bladders range between 5 bar at zero pressure and 100 bar at full turgor pressure (3-4 bar). ∈ increased with cell size (volume) at a given turgor pressure, and this volume dependence was pronounced more in the high pressure range. From the ∈ (P) characteristics, complete volume-pressure curves were obtained for Mesembryanthemum bladders and giant algal cells. The results suggest that the ∈ (P) and ∈ (V) characteristics of all plant cells are similar. The significance of the pressure and volume effects for the water relations and growth processes of plant cells is discussed briefly.