Journal Article

The Bulk Elastic Modulus and the Reversible Properties of Cell Walls in Developing <i>Quercus</i> Leaves

Takami Saito, Kouichi Soga, Takayuki Hoson and Ichiro Terashima

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 47, issue 6, pages 715-725
Published in print June 2006 | ISSN: 0032-0781
Published online June 2006 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcj042
The Bulk Elastic Modulus and the Reversible Properties of Cell Walls in Developing Quercus Leaves

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We examined the relationship between the bulk elastic modulus (ε) of an individual leaf obtained by the pressure–volume (P–V) technique and the mechanical properties of cell walls in the leaf. The plants used were Quercus glauca and Q. serrata, an evergreen and a deciduous broad-leaved tree species, respectively. We compared ε and Young’s modulus of leaf specimens determined by the stretch technique at various stages of their leaf development. The results showed that ε increased from approximately 5 to 20 MPa during leaf development, although other potential determinants of ε such as the apoplastic water content in the leaf and the diameter of a palisade tissue cells remained almost constant. ε in these two species was similar at every developmental stages, although the apparent mechanical strength of the leaf lamina and thickness of mesophyll cell walls were greater in Q. glauca. There were significant linear relationships between Young’s modulus and ε (P < 0.01; R 2 = 0.78 and 0.84 in Q. glauca and Q. serrata, respectively) with small y-intercepts. From these results, we conclude that ε is closely related to the reversible properties of the cell walls. From the estimation of ε based on a physical model, we suggest that the effective thickness of cell walls responsible for ε is smaller than the observed wall thickness.

Keywords: Bulk elastic modulus; Instron technique; Pressure–volume (P–V) curve; Reversible properties of cell walls; Stress–strain curve; Young’s modulus; Acw, cross-sectional area of the cell walls; Apal, transverse area of a cell in the first layer of palisade tissue in a leaf paradermal section; Astrip, cross-sectional area of a leaf strip for the stretch test; Aleaf, cross-sectional area in a leaf transverse section including all cell types and intercellular air spaces; E, Young’s modulus; l and l0, length of a leaf strip for the stretch test and that before the test; LA, leaf area; Lcw, perimeter length at the center of cell walls; DE, DP and DT, elastic, plastic and total compliance; LMA and DW/LA, leaf mass per area; FLE, the date of full leaf area expansion; FWC and FWCtlp, free water content and that at turgor loss point; Ns, molar concentration of solutes in the leaf cells at water saturation; Npal, number of cells in the first layer of palisade tissue in a leaf paradermal section; P–V curve, pressure–volume curve; r, radius of a spherical shell; RWC and RWCtlp, relative water content and that at turgor loss point; SW, leaf fresh weight at water saturation; Tcw and t, cell wall thickness; V, cell volume; Vcell, Vleaf and Vpal, volume of cells, leaf tissues and palisade cells; V0/Vt, the ratio of symplasmic water content to total water content in a leaf; W, width of a leaf transverse section; ε and εstretch, bulk elastic modulus and that calculated from Young’s modulus; ν, Poison’s ratio; σ, stress in the walls; Ψl,tlp and Ψπ,sat, leaf water potential at turgor loss point and osmotic potential of leaves fully saturated with water; Ψp and P, turgor pressure

Journal Article.  7515 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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