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Abstract Detail

Developmental and Structural Section

Mocko, Kerri [1], Jones, Cynthia S. [1], Nicotra, Adrienne B. [2].

Contrasting leaf shapes of Pelargonium species vary in extent of solar tracking.

Functional significance of leaf shape variation is usually attributed to effects of leaf shape on boundary layer thickness and by extension leaf temperature. While many factors affect leaf temperature in the field, under similar conditions, more highly dissected leaves are predicted to have cooler leaf temperatures than less dissected leaves. To test the extent to which leaves of varying shapes differed in leaf temperature during the South African midwinter growing season, we measured leaf temperatures over a diurnal time course for two co-occurring species of Pelargonium with similar growth forms but different leaf shapes. To examine other factors that also might influence leaf temperatures, we recorded leaf angle of inclination and angle of rotation. Despite predictions based on boundary layer theory, both species maintained leaf temperatures close to ambient throughout the day. Species did, however, vary in their ability to exhibit solar tracking. Highly dissected leaves inclined and rotated significantly more than their less-dissected counterparts. These results suggest that less-dissected leaves track the sun to maximize radiant flux density, thus increasing leaf temperatures under cool winter conditions. We expect that the thinner boundary layer of more dissected leaves also may prevent overheating in the dry summer season, but that highly dissected leaves do not pose a relative disadvantage during the winter due to their enhanced ability to track the sun.

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1 - University of Connecticut, Department of Ecology and Evolutionary Biology, 75 N. Eagleville Road, Unit 3043, Storrs, CT, 06269-3043, USA
2 - Australian National University, School of Botany and Zoology, Bld 116 Daley Rd, Canberra, ACT, 0200, Australia

South Africa
leaf shape
leaf temperature
solar tracking

Presentation Type: Poster:Posters for BSA Sections
Session: P1
Location: Event Tent/Cliff Lodge
Date: Monday, July 27th, 2009
Time: 5:30 PM
Number: P1DS005
Abstract ID:610