Thomas Boursat, Tancrède Alméras, Jonathan Barès, Léonie Molaro-Maqua, Liudmila Kozlova, Yann Boursiac, Bruno Clair
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Key message:
A first measurement of the tissue stress applied by bark and turgor pressure in the cambial region indicates that cambial growth is severely mechanically constrained by bark.
Abstract
The vascular cambium and expanding tissues are confined between the secondary xylem and the secondary phloem. Plant cell expansion is driven by turgor pressure, which generates tension in the cell wall and leads to its irreversible deformation, resulting in an increase in cell volume. When a cell is confined within surrounding tissues, these tissues exert a mechanical stress on the growing cells, referred to as tissue stress. In this context, cell expansion depends on the balance between the internal turgor pressure of the cell and the external stress applied by the surrounding tissues. Here, we present a first attempt to quantify this mechanical balance in the vascular cambium of young lime trees. The tissue stress exerted by the bark on cambial tissues was estimated from released strains and the mechanical properties of the bark measured in this study. The turgor pressure of cambial cells was directly measured using a cell pressure probe. Our analyses show that the bark applies a radial compressive stress to the vascular cambium, with a mean magnitude of − 0.17 MPa. The turgor pressure measured in actively growing cambial cells averaged 0.23 MPa. The proximity of these values suggests that cambial growth is strongly limited by the confining stress exerted by the bark. We then discuss the consequences of changes in water status (such as diurnal variations or seasonal fluctuations) on this mechanical balance and on the regulation of cambial growth.
期刊介绍：
Trees - Structure and Function publishes original articles on the physiology, biochemistry, functional anatomy, structure and ecology of trees and other woody plants. Also presented are articles concerned with pathology and technological problems, when they contribute to the basic understanding of structure and function of trees. In addition to original articles and short communications, the journal publishes reviews on selected topics concerning the structure and function of trees.
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