Shade induced changes in biomechanical petiole properties in the stoloniferous herb <Emphasis Type="Italic">Trifolium repens</Emphasis> |
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Authors: | Heidrun Huber Jan de Brouwer Hannie de Caluwe Jelmer Weijschedé Niels P R Anten |
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Institution: | (1) Department of Ecology, IWWR, Radboud University Nijmegen, Toernooiveld 1, Nijmegen, 6525 ED, The Netherlands;(2) Section of Plant Ecology and Biodiversity, Institute of Environmental Biology, Utrecht University, P.O. Box 800.84, Utrecht, 3508 TB, The Netherlands |
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Abstract: | Increased cell number and cell length both contribute to shade induced elongation of petioles which enables stoloniferous
plants to place their leaf lamina higher up in the canopy. Although petiole elongation is assumed to be beneficial, it may
also imply costs in terms of decreased biomechanical stability. We test the hypothesis that shade induced elongation changes
the biomechanical properties of petioles and that the underlying mechanisms, cell division and cell elongation, differentially
affect biomechanical properties. This was done by subjecting 14 genotypes differing in the relative contribution of cell size
and cell number to shade induced elongation responses to high light conditions and to simulated canopy shade. Developmental
traits (cell size and cell number), morphological traits characterizing the petioles, as well as biomechanical characteristics
were measured. Our results show that, comparable to stems of non-clonal plants, the rigidity of a petiole’s tissue (the Young’s
modulus) increases, leading to increased flexural stiffness of petioles subjected to shading. Increased flexural stiffness
proved to be associated with increased performance under shaded conditions. Our results also indicate that cell number affected
the material properties and the flexural stiffness of petioles. However, the degree and pattern of the effects differed between
light environments. Shade induced increase in cell number translated into shade induced increase of Young’s modulus and flexural
stiffness. Genotypes producing relatively larger cells under shaded conditions experienced a decrease in tissue rigidity.
In concert our results indicate that the pattern of selection on flexural stiffness, and thereby also on shade induced changes
of cell number and cell size differs among light environments.
An erratum to this article can be found at |
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Keywords: | Cell number Cell size Flexural stiffness Petiole elongation Shade induced plasticity Stoloniferous plants Young’ s modulus |
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