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Paleobotanical Section

Boyce, C. Kevin [1], Zwieniecki, Maciej A. [2], Holbrook, Noel [3].

Vascular anatomy and leaf hydraulic function.

Beyond the overall architecture of leaf vein networks, the detailed anatomy of individual veins may strongly impact hydraulic function and thereby the range of morphologies that can be supported. The importance of vascular anatomy is being investigated with two approaches: modeling of the influence of hydraulic variables on morphological possibilities and anatomical studies of living plants. Modeling has involved development of a functional design space based upon hydraulic parameters. Rather than focusing upon morphology as empirically documented or geometrically possible, an iterative model has been used to determine the relative leaf sizes and shapes that are functionally possible along several hydraulic variables in a single-veined leaf. Evaluation of this simple system for the possible leaf morphologies for which the entire lamina can be supplied with sufficient water defines a functional design space that includes all single-veined leaf shapes found in nature. This exercise demonstrates that different hydraulic parameters have dissimilar influences upon leaf size and shape and provides insight into patterns of morphological and anatomical evolution documented in the fossil record. For example, the sequences of morphological change repeated during the evolution of leaves in independent Paleozoic lineages may represent a rise in developmental complexity that allowed a more physiologically permissive set of morphological possibilities. This has informed anatomical investigations into how vascular anatomy varies across extant plants of different morphologies and how hydraulic properties vary proximally to distally within individual leaf veins. Such anatomical gradients may play important roles in determining the range of supportable leaf morphologies, but the capacity for such anatomical complexity appears to vary across different plant lineages.

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1 - University of Chicago, Department of Geophysical Sciences, 5734 S. Ellis Avenue, Chicago, Illinois, 60637, USA
2 - Arnold Arboretum of Harvard University, 125 Arborway, Jamaica Plain, Massachusetts, 02130, USA
3 - Harvard University, 16 Divinity Avenue, Cambridge, Massachusetts, 02138, USA

none specified

Presentation Type: Oral Paper
Session: 22-2
Location: 404/Hilton
Date: Monday, August 15th, 2005
Time: 3:45 PM
Abstract ID:389

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