How Tough are Sclerophylls?

Turner, I. M.; Choong, M. F.; Tan, Hugh Tiang Wah; Lucas, Peter W.

doi:10.1006/anbo.1993.1043

Cited by 30 publications

(30 citation statements)

References 13 publications

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“…8 The relationship between Component 1 scores from the PCA and leaf specific mass (open triangles forest species, filled circles intermediate species, filled triangles heath species). The two collections of Banksia marginata are indicated by arrows Choong et al 1992;Turner et al 1993). However, these differences in magnitude between lamina and higher-order veins may vary among leaf types, probably more so in malacophylls than in sclerophylls.…”

Section: Methodological Issuesmentioning

confidence: 97%

“…Most studies of leaf mechanical properties have not been directed at sclerophylly per se, and therefore have had relatively little influence on an understanding of this leaf form and its functional significance. Some mechanical properties of sclerophyllous leaves have been examined in the pioneering work of Choong et al (1992) and Turner et al (1993). The latter is the only work known to us that has examined leaf mechanical properties in any detail in plants from mediterraneantype climates where sclerophylly predominates.…”

Section: Introductionmentioning

confidence: 99%

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Characterising sclerophylly: some mechanical properties of leaves from heath and forest

Edwards¹,

Read²,

Sanson³

2000

Oecologia

103

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Although sclerophylly is widespread through the world and is often the dominant leaf-form in mediterranean climates, the mechanical properties of sclerophyllous leaves are poorly understood. The term "sclerophyllous" means hard-leaved, but biologists also use terms such as tough, stiff and leathery to describe sclerophyllous leaves. The latter term has no precise definition that allows quantification. However, each of the former terms is well-defined in materials engineering, although they may be difficult or sometimes inappropriate to measure in leaves because of their size, shape or composite and anisotropic nature. Two of the most appropriate and practically applicable mechanical properties of sclerophyllous leaves are "strength" and "toughness", which in this study were applied using punching, tearing and shearing tests to 19 species of tree and shrub at Wilson's Promontory, Australia. The results of these tests were compared with leaf specific mass (LSM) and a sclerophylly index derived from botanists' ranks. Principal components analysis was used to reduce the set of mechanical properties to major axes of variation. Component 1 correlated strongly with the botanists' ranks. Overall, leaves ranked as sclerophyllous by botanists were both tough and strong in terms of punching and tearing tests. In addition, tough and strong leaves typically had high toughness and strength per unit leaf thickness. There was also a significant correlation between component 1 and LSM. Although more detailed surveys are required, we argue that sclerophylly should be defined in terms of properties that have precise meanings and are measurable, such as toughness and strength, and that relate directly to mechanical properties as implicit in the term.

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Section: Methodological Issuesmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Characterising sclerophylly: some mechanical properties of leaves from heath and forest

Edwards¹,

Read²,

Sanson³

2000

Oecologia

103

View full text Add to dashboard Cite

show abstract

“…Despite the uncertainty surrounding the exact physical nature of fracture when punching, many authors have consistently found the test to provide correlations with physical aspects of leaf biology (e.g. Larsson & Ohmart, 1988 ;Aide & Zimmerman, 1990 ;D'Angelo & Webster, 1992 ;Turner et al, 1993 ;Bergvinson et al, 1994 ;Grubbs & Cummins, 1994). Therefore the punch test may be detecting ecologically significant variation in the fracture properties of leaves.…”

Section: mentioning

confidence: 99%

Methods of assessing leaf‐fracture properties

1999

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Numerous authors have attempted to quantify the physical properties of leaves in relation to aspects of leaf ecology, including decomposition, sclerophylly, herbivory, and leaf function and longevity. This paper examines the relative merits of the punch-and-die, tearing and shearing tests for assessing leaf physical properties. We conducted a series of these three mechanical tests on leaves of Solanum laciniatum, and determined the effect of various test parameters on the measurement of fracture properties. For the punch-and-die test, the parameters considered were machine speed, clearance between the punch and the die, edge definition of the punch, and area of the punch. Aspects of the tearing test examined were notch length, end effects, and length-to-width requirements of test strips, and for shearing tests the effects of blade proximity, angle and sharpness were investigated. All the test parameters investigated were found significantly to affect the assessment of leaf-fracture properties. In addition, fracture properties were found to vary significantly within leaves. Some general principles for designing and implementing tests are outlined. This study suggests that while punching and shearing tests are useful means of quantifying leaf fracture properties, the value of the tearing test may be reduced as it is most constrained by the biological nature of the test material.

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“…Other methods have been reported for or as mechanical ' sleeves' around major and minor measuring sclerophylly, such as the Loveless method leaf veins (Esau, 1977). In this case, leaves become (Loveless, 1962) relating the percentage of crude typically 'coriaceous to the touch, breaking when fibre plus percentage of crude protein to leaf d. wt, or the metbod described by Turner et al (1993), different subsequent days, was measured using tbe measuring tbe mechanical strength of leaf blade. We pressure chamber.…”

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confidence: 99%

Is sclerophylly of Mediterranean evergreens an adaptation to drought?

1997

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SUMMARYThe potential role of sclerophylly (leaf hardness and rigidity) in the control of leaf dehydration and rehydration was investigated in two sclerophylls {Viburnum tinus and Ilex aquifolium) and two non-sclerophylls (Hedera helix ssp. helix and Sambucus nigra). After leaves were dehydrated in the pressure chamber, water transport from the apoplast (mainly consisting of xylem conduits and mechanical cells) to symplast was detected 15 min from pressure release, in terms of a spontaneous increase in leaf water potential (!F,). This !P, increase was much larger in sclerophylls than in non-sclerophylls.Positive pressures applied to leaves simulated the tensions developing in the leaf apoplast under water stress conditions, causing water to be expelled from leaf xylem conduits and mechanical cells and transferred to the leaf symplast, thus leading to symplast rehydration and to the consequent W^ increase.No correlation was found between the leaf modulus of elasticity at full turgor or the degree of sclerophylly (in terms of the ratio of leaf d. wt to surface area) and the characteristic rehydration time of the leaves, i.e. between the two main parameters expressing the rigidity of the leaf blade and the rate of leaf rehydration. However, when changes in !F, were measured as a function of leaf water deficit (RWD), equal W^s corresponded with larger RWDs during leaf rehydration than during leaf dehydration in the two non-sclerophylls. In particular, the two sclerophylls showed rehydration of their leaf apoplast and symplast completely and simultaneously. By contrast, the two non-sclerophylls showed a persisting water loss, localized, it is likely, in their xylem conduits and mechanical cells.In other words, the two sclerophylls did not recover from water loss more rapidly than non-sclerophylls but they recovered from xylem cavitation more completely. The major elasticity of the cavitation strain shown by the two sclerophylls studied was interpreted as of advantage to plants subjected to diurnal large drops in W^ followed by nocturnal recovery. This is the case in Mediterranean sclerophylls growing in areas characterized by high humidity of the air condensing on the soil at night. The same mechanism of cavitation recovery, however, would be useless in very xeric areas.The hypothesis is advanced that sclerophylly of Mediterranean species may derive from similar anatomical structures developed in species formerly adapted to more humid environments which later migrated to more arid zones.

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How Tough are Sclerophylls?

Cited by 30 publications

References 13 publications

Characterising sclerophylly: some mechanical properties of leaves from heath and forest

Characterising sclerophylly: some mechanical properties of leaves from heath and forest

Methods of assessing leaf‐fracture properties

Is sclerophylly of Mediterranean evergreens an adaptation to drought?

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