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Pteridological Section/AFS

Husby, Chad E [1], Palow, Danielle T. [2].

Biomechanics of Equisetum giganteum L. in the Atacama Desert and northwestern Argentina.

Equisetum giganteum is one of the largest living members of a unique pteridophyte group. Its hollow upright stems, reinforced by nodal thickenings and septa, can grow to over 4 m in height. However, the relatively small diameters of E. giganteum stems (generally less than ~4 cm) pose a challenge to their mechanical stability against buckling. We measured the bending properties of E. giganteum stems growing under contrasting environmental conditions in South America. In the extremely arid Atacama Desert, E. giganteum grows in isolated river valleys, whereas in northwestern Argentina this species grows in humid environments. We found that, although E. giganteum in northern Chile and northwestern Argentina grow in very different environments and have stems of different appearance, their average Young's moduli of elasticity (E) were similar (4.17 GPa in Chile and 3.96 GPa in Argentina). The log-log linear relationships we found between the second moment of area (I) and flexural stiffness (EI) are consistent with earlier investigators' characterization of E. giganteum as having semi-self-supporting habit, relying on synergistic support among neighboring stems to prevent buckling. We also found a lack of relationship between I and E that is consistent with this growth habit. The similar scaling relationships between stem diameter and stem wall thickness for the Chilean and Argentinian plants suggests that spatial distribution of stem tissue is little affected by the different environments of these regions. However, the values of E found in this study were nearly three times higher than the values measured in a prior study of a greenhouse-grown E. giganteum clone, suggesting that highly sheltered growing conditions can reduce the E of E. giganteum stems.

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Related Links:
Giant Horsetails website: contains detailed information on the biology of Equisetum gigantetum , E. myriochaetum and E. x schaffneri

1 - Florida International University, Department of Biological Sciences, 11200 Sw 8Th Street, Oe167, Miami, Florida, 33199, USA
2 - University of Florida, Department of Botany, 220 Bartram Hall, P.O. Box 118526, Gainesville, Florida, 32611-8526, USA

modulus of elasticity
flexural stiffness
Giant horsetail.

Presentation Type: Oral Paper
Session: 5-8
Location: 602/Hilton
Date: Monday, August 15th, 2005
Time: 11:15 AM
Abstract ID:43

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