Leaf fracture toughness and sclerophylly: their correlations and ecological implications

Choong, M. F.; Lucas, Peter W.; Ong, Joy; Pereira, Barry P.; Tan, Hugh Tiang Wah; Turner, I. M.

doi:10.1111/j.1469-8137.1992.tb01131.x

Cited by 282 publications

(243 citation statements)

References 66 publications

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“…Furthermore, seed shells have no transport function and can have much higher densities than woods, enabling predictions about the potential for the toughening mechanism to be tested more fully. The development of woody toughness in ripening seeds, pods and maturing leaves has value in studies of mammalian feeding behaviour because toughness may form one of the principal methods of detecting high fibre (Choong et al 1992 ;Hill & Lucas 1996). Experiments that dissociate the cost of cell wall fracture from woody toughness show exactly why fibre content is not proportional to toughness.…”

Section: Discussionmentioning

confidence: 99%

The toughness of secondary cell wall and woody tissue

Lucas

Tan

Cheng

1997

Phil. Trans. R. Soc. Lond. B

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SUMMARYThe ' across grain ' toughness of 51 woods has been determined on thin wet sections using scissors. The moisture content of sections and the varying sharpness of the scissor blades had little effect on the results. In thin sections ( 0.6 mm), toughness rose linearly with section thickness. The intercept toughness at zero thickness, estimated from regression analysis, was proportional to relative density, consistent with values reported for non-woody plant tissues. Extrapolation of the intercept toughness of these woods and other plant tissues\materials to a relative density of 1.0 predicted a toughness of 3.45 kJ m −# , which we identify with the intrinsic toughness of the cell wall. This quantity appears to predict published results from IC tests on woods and is related to the propensity for crack deflection. The slope of the relationship between section thickness and toughness, describing the work of plastic buckling of cells, was not proportional to relative density, the lightest (balsa) and heaviest (lignum vitae) woods fracturing with less plastic work than predicted. The size of the plastic zone around the crack tip was estimated to be 0.5 mm in size. From this, the hypothetical overall toughness of a thick ( 1 mm) block of solid cell wall material was calculated as 39.35 kJ m −# , due to both cell wall resistance (10 %) and the plastic buckling of cells (90 %). This value successfully predicts the toughness of most commercial woods (of relative densities between 0.2 and 0.8) from ' work area ' tests in tension and bending. Though density was the most important factor, both fibre width\fibre length (in hardwoods) and lignin\cellulose ratios were negatively correlated with the work of plastic buckling, after correcting for density. At low densities, the work of plastic buckling in the longitudinal radial (LR) direction exceeded that in longitudinal tangential (LT), but the reverse was true for relative densities above 0.25. This could be attributed to the direction of rays. Density for density, the toughness of temperate hardwoods tested was about 20 % lower than that of tropical hardwoods. This is probably due to the much greater number of vessels in temperate hardwoods. Vessels appear either not to display buckling behaviour during fracture at all or to collapse cheaply. These general results have applications to other plant tissues.

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Section: Discussionmentioning

confidence: 99%

The toughness of secondary cell wall and woody tissue

Lucas

Tan

Cheng

1997

Phil. Trans. R. Soc. Lond. B

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“…The SLM is known to be correlated with relative growth rate under some environmental conditions (Poorter & Remkes, 1990) ; with leaf gas exchange (Mooney et al, 1978 ;Field & Mooney, 1983 ;Ellsworth & Reich, 1992) ; with seedling regeneration (Shipley et al, 1989 ;Maranon & Grubb, 1993) ; and with leaf palatability (Lucas & Pereira, 1990 ;Choong et al, 1992). Thus, SLM is implicated in ecological processes (growth and survival) that are key to evolutionary fitness.…”

Section: mentioning

confidence: 99%

Leaf structure and specific leaf mass: the alpine desert plants of the Eastern Pamirs, Tadjikistan

P’yankov¹,

Kondratchuk²,

Shipley³

1999

New Phytologist

110

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This study examines interrelationships between eight leaf attributes (specific leaf mass, area, dry mass, lamina thickness, mesophyll cell number per cm#, mesophyll cell volume, chloroplast volume, and number of chloroplasts per mesophyll cell) in field-grown plants of 94 species from the Eastern Pamir Mountains, at elevations between 3800 and 4750 m. Unlike most other mountain areas, the Eastern Pamirs, Karakorum system, Tadjikistan provide localities where low temperatures and radiation combine with moisture stress at high altitudes. For all the attributes measured, significant differences were found between plants with different mesophyll types. Leaves with dorsiventral palisade structure (dorsal palisade, ventral spongy mesophyll cells) had thicker leaves with larger but fewer mesophyll cells, containing more and larger chloroplasts. These differences in mesophyll type are reflected in differences in the total surface of mesophyll cells per unit leaf area (A mes \A) or volume (A mes \V ). Plants with isopalisade leaf structure (palisade cells under both dorsal and ventral surfaces) are more commonly xerophytes and their increased values of A mes \A and A mes \V decrease CO # mesophyll resistance, which is an important adaptation to drought. Path analysis shows the critical importance of mesophyll cell volume in leading to the covariance between the different leaf attributes and hence to specific leaf mass (SLM), even though mesophyll cell volume is not itself strongly correlated with SLM. This is because mesophyll cell volume increases SLM through its effects on leaf thickness and chloroplast number per cell, but decreases SLM through its negative effect on mesophyll cell density.

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“…Extensive literature exists relating the physical properties of leaves to their ecology, covering topics such as herbivory (Coley, 1983 ;Raupp, 1985 ;Nichols-Orians & Shultz, 1990 ;Choong, 1996), decomposition (Arsuffi & Suberkropp, 1984 ;Gallardo & Merino, 1993), sclerophylly (Medina et al, 1990 ;Choong et al, 1992 ;Turner, 1994) and leaf longevity (Reich et al, 1991). Although fracture properties are measured routinely in engineering, determining the fracture properties of plants, and of biomaterials in general, is complicated for the following reasons.…”

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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Leaf fracture toughness and sclerophylly: their correlations and ecological implications

Cited by 282 publications

References 66 publications

The toughness of secondary cell wall and woody tissue

The toughness of secondary cell wall and woody tissue

Leaf structure and specific leaf mass: the alpine desert plants of the Eastern Pamirs, Tadjikistan

Methods of assessing leaf‐fracture properties

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