Schwendemann, Andrew , Taylor, Thomas , Taylor, Edith .
Hydraulics in Fossil Plants from the Permian and Triassic of
Water transport in plants is an important physiological topic that has received a lot of attention, including studies that focus on water transport in fossil plants. To date, this work has primarily concentrated on water transport through fossil stems. Fossilized leaves are more common and represent an excellent opportunity to study plant paleophysiology due to the many interactions between leaves and their environment. Leaf venation architecture varies greatly across plant species and is often used to differentiate leaf fossils into separate morphotaxa. Venation architecture plays an important role in leaf biomechanical support, the delivery of nutrients and photosynthates, and in hydraulic supply. In turn, leaf hydraulic supply influences the maximum photosynthetic rate of the plant as well as the amount of water lost to the atmosphere. Although hydraulic studies in plants mostly focus on stem hydraulics, leaves contribute at least one-fourth of the total resistance to water movement in the whole plant. In general, water conductance in a leaf increases with increased midrib conductivity and minor vein density. Although the Hagen-Poiseuille equation can calculate individual vein conductivity,it does not incorporate the venation architecture of the whole leaf. Here, a spatially explicit model for studying the leaf hydraulics of extant angiosperms is applied to fossil leaves from the Permian and Triassic of Antarctica. Leaf morphotypes included in this study include Glossopteris, Dicroidium, and Heidiphyllum.Such an analysis allows for the comparison of relative hydraulic construction costs and maximum photosynthetic rates. Due to the inherent assumptions of the conductance model and the inherent incompleteness associated with fossils, absolute values are impossible to obtain. The model does, however, allow for comparisons to be made to leaf types across latitudinal gradients and through time. This model will be used to study potential physiological changes in leaf types at different paleolatitudes as well as examine possible physiological reasons for the dominance of some plant groups.
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1 - University of Kansas, Ecology and Evolutionary Biology, 1200 Sunnyside Avenue, Haworth Hall, Lawrence, KS, 66045-7534, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Lindell C/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 10:30 AM