Sack, Lawren , Scoffoni, Christine , Frole, Kristen , McKown, Athena D. , Havran, J. Christopher .
The scaling of leaf venation architecture: laws, functional implications and paleo-applications.
Leaf venation architecture varies enormously among modern plant species and across the fossil record. Recent work has shown that this diversity in venation has consequences for leaf and whole-plant hydraulic capacity, for leaf biomechanical support, and for leaf tolerance of vein damage. However, little work so far has focused on determining if the leaf venation architecture follows general design principles. We asked whether venation traits are generally linked with leaf size and shape, which are evolutionary labile traits, extremely variable across species. We chemically cleared leaves from (1) diverse Panamanian rainforest tree species, from (2) herbaceous and woody Hawaiian violets (Viola, Violaceae), collected in bogs, forest and cliff habitats on three islands, and from (3) maple species of North America, Europe and Asia (Acer, Sapindaceae) growing in the Arnold Arboretum, Massachusetts. We quantified aspects of leaf venation architecture, including densities (length/area) of veins of each order, and branching angles. We determined trait variation with leaf size, within and across species, and tested the data against scaling models based on simple geometric and/or developmental constraints. We found novel scaling relationships, including a general negative scaling between major vein densities and leaf size, both within and across species. Consequently, smaller leaves have greater major vein density, pointing to a potential tendency toward greater tolerance of vein damage or blockage. By contrast, minor vein density was independent of leaf size and shape, indicating that hydraulic capacity and gas exchange would also be unconstrained by leaf size and shape. Our findings are consistent with the major and minor venation systems developing and evolving semi-independently, according to different selection pressures. Additionally, our findings have potential applications to paleobotany: these new scaling relationships may allow predictions of intact leaf size and shape from fossil leaf fragments, given information of their venation characters.
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1 - University of California, Los Angeles, Ecology and Evolutionary Biology, 621 Charles E. Young Drive, Los Angeles, CA, 90095, USA
2 - University of Bordeaux, Avenue des Facultés, Talence, 33405, France
3 - University of Hawaii, Botany Department, 3190 Maile Way, Honolulu, Hawaii, 96822
4 - Ohio University, Department of Environmental and Plant Biology, Porter 315, Athens, OH, 45701, U.S.A.
Barro Colorado Island
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 28th, 2008
Time: 4:00 PM