Lopez-Portillo, Jorge , Ewers, Frank W. , Angeles, Guillermo .
Embolism vulnerability and reversal in the xylem of two mangrove species.
HYDRAULIC conductivity, resistance to embolism, and nighttime embolism reversal were measured in Conocarpus erectus and Avicennia germinans at the La Mancha Lagoon in the state of Veracruz, Mexico. Care was taken to measure conductivity with perfusion solutions that were similar in salinity to the xylem sap, to minimize hydrogel effects. Based upon the whole shoot dehydration technique, Avincennia was more resistant to embolism (P50 = -5.7 MPa) than was Conocarpus (P50 = -3.7 MPa). However, Avicennia had much lower xylem specific conductivity, lower leaf specific conductivity, and lower (more negative) pre-dawn and midday pressure potentials than Conocarpus. For each species, during both the rainy and dry seasons, measurements of predawn and midday embolism (percent loss conductivity; PLC) were done at both a relatively high saline site and a low saline site. During the rainy season, the PLC values were higher at midday than at predawn at both sites for Conocarpus and at a low saline site for Avicennia. During the dry season, the PLC values were not significantly different between midday and predawn for both species at all sites. Apparent nighttime embolism reversal occurred in both species only when predawn water potentials were less negative than about -1.6 MPa. While Avicennia was more resistant to embolism, embolism reversal was rarer in this species perhaps due to its chronically lower water potentials.
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1 - Instituto de Ecología, A. C., Departamento Ecología Vegetal, km 2.5 antigua carretera a Coatepec No. 351, Congregación El Haya, Xalapa, Veracruz, 91070, Mexico
2 - Michigan State University, Department of Plant Biology, 166 Plant Biology Building, East Lansing, Michigan, 48824-1312, USA
3 - Instituto de Ecología, A.C., Unidad de Recursos Forestales, Km 2.5 ant. carr. a Coatepec, Xalapa, Veracruz, 91070, Mexico
Presentation Type: Oral Paper:Papers for Sections
Location: 134/Performing Arts Center
Date: Monday, July 31st, 2006
Time: 8:45 AM