Ewers, Frank W. , Lopez-Portillo, Jorge , Angeles, Guillermo , Peter, Hietz .
The dual roles of non-glandular foliar trichomes in the mangrove tree Avicennia germinans.
A dense indumentum of non-glandular uniseriate trichomes characterizes the abaxial surface of leaves of Avicennia. The trichomes each have a non-living cap cell and completely cover the stomates, which are strictly abaxial. At the Sontecomapan Lagoon in Veracruz, Mexico, a mangrove site with unusually high rainfall and freshwater influx, plants have some leaves that are glabrous, lacking indumentum, some leaves that are hairy, with the abaxial surface completely covered with indumentum and others with some portion of their adbaxial surface covered with indumentum. We tested the possible role of the trichomes in conserving water. With transplants from this site as well as from La Mancha Lagoon, a site where plants present only hairy leaves, we found that the rates of transpiration, stomatal conductance, and photosynthesis were all higher in the hairy than the glabrous leaves. Stomatal density did not differ between hairy and glabrous leaves. In dehydration experiments with isolated leaves, we found that fully saturated hairy leaves initially lost water more quickly than glabrous leaves, but retained water more effectively during the dehydration phase ranging from about 90% to 40% of their saturated fresh weight. In rehydration experiments the hairs of the indumentum allowed for rapid uptake of water but it is not clear whether the water gets into the leaf proper. It appears that at higher (less negative) water potentials, the trichomes allow the stomates to remain open longer, enhancing photosynthesis, while under drier conditions the trichomes prevent excess water loss. The only advantage we found to glabrous leaves is that they have greater specific leaf area (greater leaf area per dry weight), perhaps allowing for faster growth.
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1 - Michigan State University, Department of Plant Biology, 166 Plant Biology Building, East Lansing, Michigan, 48824-1312, USA
2 - Instituto de Ecología, A. C., Departamento Ecología Vegetal, km 2.5 antigua carretera a Coatepec No. 351, Congregación El Haya, Xalapa, Veracruz, 91070, Mexico
3 - Instituto de Ecología, A.C., Unidad de Recursos Forestales, Km 2.5 ant. carr. a Coatepec, Xalapa, Veracruz, 91070, Mexico
4 - Universitat fur Bodenkultur, Institut fur Botanik, Gregor Mendel Strasse, 33, A-1180, Wien, , Austria
Presentation Type: Oral Paper:Papers for Sections
Location: 134/Performing Arts Center
Date: Monday, July 31st, 2006
Time: 8:30 AM