© 2007 Heron Publishing—Victoria, Canada
Mechanical analysis of the strains generated by water tension in plant stems. Part I: stress transmission from the water to
the cell walls
Tancrède Alméras (1, 2) and Joseph Gril (3)
1. INRA-UMR Ecofog, Campus Agronomique, BP 316, 97379 Kourou Cedex, French Guiana, France / 2. Corresponding author (t_almeras@hotmail.com) / 3. LMGC, Université Montpellier 2, Montpellier, France / Received November 24, 2006; accepted March 10, 2007; published online August 1, 2007
Summary
Plant tissues shrink and swell in response to changes in water pressure. These strains can be easily measured, e.g., at the
surface of tree stems, to obtain indirect information about plant water status and other physiological parameters. We developed
a mechanical model to clarify how water pressure is transmitted to cell walls and causes shrinkage of plant tissues, particularly
in the case of thick-walled cells such as wood fibers. Our analysis shows that the stress inside the fiber cell walls is lower
than the water tension. The difference is accounted for by a stress transmission factor that depends on two main effects.
The first effect is the dilution of the stress through the cell wall, because water acts at the lumen border and is transmitted
to the outer border of the cell, which has a larger circumference. The second effect is the partial conversion of radial stress
into tangential stress. Both effects are quantified as functions of parameters of the cell wall structure and its mechanical
properties.
Keywords:
biomechanics, cell mechanics, diurnal strains, mechanical model, multilayer cylinder, stress transmission factor.
