Field measurements of gas exchange in Avicennia marina and Bruguiera gymnorrhiza |
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Authors: | Naidoo G. Rogalla H. von Willert D.J. |
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Affiliation: | (1) Department of Botany, University of Durban-Westville, Private Bag X54001, Durban, South Africa;(2) Institut für ökologie der Pflanzen, Westfälische Wilhelms Universität, Hindenburgplatz 55, 48143 Münster, Germany |
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Abstract: | Diurnal gas exchange characteristics were measured simultaneously in two mangrove species, Avicennia marina and Bruguiera gymnorrhiza, over 7 d in summer (February–March), to compare their productivity. The study was undertaken in the Beachwood Mangroves Nature Reserve, Durban, South Africa, using fully expanded leaves of young and mature trees at the top of the canopy. Gas exchange was strongly influenced by photosynthetic photon flux density (PPFD), leaf temperature and the accompanying leaf to air vapour pressure deficit ( w). Carbon dioxide exchange was saturated at a PPFD of about 600 mol m-2s-1 in B. gymnorrhiza compared to 800 mol m-2s-1 in A. marina. Maximal CO2 exchange occurred between 12h00 and 14h00 and was consistently greater in A. marina (8.8 mol m-2s-1) than in B. gymnorrhiza (5.3 mu;mol m-2s-1). Mean internal CO2 concentrations ( ci) were 260 l l-1 in A. marina and 252 l l-1 in B. gymnorrhiza. Photorespiratory activity was 32% in A. marina and 30% in B. gymnorrhiza. Mean water use efficiency (WUE) was 8.0 mol mmol-1 in A. marina and 10.6 mol mmol-1 in B. gymnorrhiza. Diurnal leaf water potentials ranged from –0.8 to –3.5 MPa and were generally lower in A. marina. |
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Keywords: | conductance mangrove photosynthesis productivity water potential |
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