Mechanical analysis of the strains generated by water tension in plant stems. Part II: strains in wood and bark and apparent
compliance
Tancrède Alméras (1)
1. INRA-UMR Ecofog, Campus Agronomique, BP 316, 97379, Kourou Cedex, French Guiana, France () / Received November 24, 2006; accepted May 5, 2008; published online August 1, 2008
Summary
Tree stems shrink in diameter during the day and swell during the night in response to changes in water tension in the xylem.
Stem shrinkage can easily be measured in a nondestructive way, to derive continuous information about tree water status. The
relationship between the strain and the change in water tension can be evaluated by empirical calibrations, or can be related
to the structure of the plant. A mechanical analysis was performed to make this relationship explicit. The stem is modeled
as a cylinder made of multiple layers of tissues, including heartwood, sapwood, and inner and outer bark. The effect of changes
in water tension on the apparent strain at the surface of a tissue is quantified as a function of parameters defining stem
anatomy and the mechanical properties of the tissues. Various possible applications in the context of tree physiology are
suggested.
