WIT Press

The Optimized Shape Of A Leaf Petiole


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D. Pasini & V. Mirjalili


A plant leaf is generally composed of a petiole and a leaf blade. The petiole connects the leaf blade to the plant stem and, from a structural viewpoint, it resembles a cantilever beam. Petiole design is driven by the minimum use of material to withstand a combined torsion and bending load. The cross-section has a transverse size decreasing lengthwise and has a grooved shape. This paper examines the structural efficiency of the petiole shape. Ten petiole specimens of dicotyledonous plants have been investigated. Continuum mechanics and dimensionless factors are used to model the stiffness properties of the petioles. The results of the characterization are visualized on maps that contrast petiole efficiency to that of reference cross-sections. Nature shapes the petiole material to secure the best trade off between torsional compliance and flexural stiffness. Keywords: leaf petiole, structural efficiency, optimized shape, torsional compliance, bending stiffness. 1 Introduction Plants are complex systems that perform several vital functions. Their organs work in synergy to govern a variety of tasks, such as mineral absorption, water supply, photosynthesis, food storage, and structural support. During growth, the plant organs that interface with the environment receive different stimuli from light, gravity, touch, as well as from change of soil salinity and stress concentration. As a response to these factors, the plant adapts its morphology. Plants have a large variety of colours, forms and size, which make them attractive. Appearance, though, is just one among the remarkable features. Plants are designed to multi-function as well as to support a variety of loading configurations by using the least amount of bio-material [1].


leaf petiole, structural efficiency, optimized shape, torsional compliance, bending stiffness.