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.
