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Anatomy and Morphology |
2 Department of Botany, Miami University, Oxford, Ohio 45056 USA 3 Department of Paper and Chemical Engineering, Miami University, Oxford, Ohio 45056 USA
ABSTRACT
Differences in the flexibility of Pinus nigra and P. resinosa leaves can be used to discriminate these two similarly looking pine species from one another. When bent along the longitudinal axis, P. resinosa leaves snap, while P. nigra leaves appear flexible. This useful field test has had no known biophysical or anatomical explanation until now. Analysis of the first order mechanics of bending and buckling of the pine needles was used to elucidate any important anatomical differences between these two species that can account for their different biophysical behaviors when bent. Neither the cross section of the total leaf area nor the inner core area between the two species differed significantly. Differences in the pattern of cell wall thickening and lignification of the endodermal layer of the inner core of the leaves best explain the differences in bending behavior. Thus, subtle variation in anatomy can influence the biophysical properties of naturally occurring structures, which in turn could have important implications for the engineering of manufactured objects.
Key Words: anatomy biophysics brittle flexible leaves Pinaceae Pinus sandwich composite beams
Received for publication 3 April 2008. Accepted for publication 9 July 2008.
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