Journal Article

Effects of Light and Nutrient Availability on Leaf Mechanical Properties of <i>Plantago major</i>: A Conceptual Approach

Yusuke Onoda, Feike Schieving and Niels P.R. Anten

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 101, issue 5, pages 727-736
Published in print April 2008 | ISSN: 0305-7364
Published online February 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn013
Effects of Light and Nutrient Availability on Leaf Mechanical Properties of Plantago major: A Conceptual Approach

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Leaf mechanical properties, which are important to protect leaves against physical stresses, are thought to change with light and nutrient availabilities. This study aims to understand phenotypic changes of leaf mechanical properties with respect to dry mass allocation and anatomy.

Methods

Leaf lamina strength (maximum force per unit area to fracture), toughness (work to fracture) and stiffness (resistance against deformation) were measured by punch-and-die tests, and anatomical and physiological traits were determined in Plantago major plants grown at different light and nutrient availabilities. A conceptual approach was developed by which punch strength and related carbon costs can be quantitatively related to the underlying anatomical and morphological traits: leaf thickness, dry-mass allocation to cell walls and cell-wall-specific strength.

Key Results

Leaf lamina strength, toughness and stiffness (all expressed on a punch area basis) increased with light availability. By contrast, nutrient availability did not change strength or toughness, but stiffness was higher in low-nutrient plants. Punch strength (maximum force per unit punch area, Fmax/area) was analysed as the product of leaf mass per area (LMA) and Fmax/leaf mass (= punch strength/LMA, indicating mass-use efficiency for strength). The greater strength of sun leaves was mainly explained by their higher LMA. Shade leaves, by contrast, had a higher Fmax/leaf mass. This greater efficiency in shade leaves was caused by a greater fraction of leaf mass in cell walls and by a greater specific strength of cell walls. These differences are probably because epidermis cells constitute a relatively large fraction of the leaf cross-section in shaded leaves. Although a larger percentage of intercellular spaces were found in shade leaves, this in itself did not reduce ‘material’ strength (punch strength/thickness); it might, however, be important for increasing distance between upper and lower epidermis per unit mass and thus maintaining flexural stiffness at minimal costs.

Conclusions

The consequences of a reduced LMA for punch strength in shaded leaves was partially compensated for by a mechanically more efficient design, which, it is suggested, contributes importantly to resisting mechanical stress under carbon-limited conditions.

Keywords: Cell walls; cost–benefit; defence; leaf biomechanics; leaf mass per area; nitrogen; Plantago major; punch-and-die test; stiffness; strength; toughness

Journal Article.  6552 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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