Journal
FUNCTIONAL PLANT BIOLOGY
Volume 48, Issue 7, Pages 732-742Publisher
CSIRO PUBLISHING
DOI: 10.1071/FP21087
Keywords
C-3; CAM; Crassulacean acid metabolism; Tillandsia fasciculata; Werauhia sanguinolenta; photosynthetic pathway; gas exchange; epiphyte; oxygen isotopes; altitudinal gradient; mesocosm
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Funding
- British Council
- government of Panama through the Senacyt-IFARHU 2005-2010 program
- Fondo Sectorial SEP-CONACYT [221490]
- NERC [NE/M001946/1]
- Smithsonian Tropical Research Institute
- Natural Environment Research Council [NE/M001946/1] Funding Source: researchfish
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This study used stable isotopes to investigate the distributions of CAM and C-3 epiphytic bromeliads across an altitudinal gradient in western Panama and their water balance. The results demonstrated significant differences in leaf water among different altitudes and seasons.
The distributions of CAM and C-3 epiphytic bromeliads across an altitudinal gradient in western Panama were identified from carbon isotope (delta C-13) signals, and epiphyte water balance was investigated via oxygen isotopes (delta O-18) across wet and dry seasons. There were significant seasonal differences in leaf water (delta O-18(lw)), precipitation, stored 'tank' water and water vapour. Values of delta O-18(lw) were evaporatively enriched at low altitude in the dry season for the C-3 epiphytes, associated with low relative humidity (RH) during the day. Crassulacean acid metabolism (CAM) delta O-18(lw) values were relatively depleted, consistent with water vapour uptake during gas exchange under high RH at night. At high altitude, cloudforest locations, C-3 delta O-18(lw) also reflected water vapour uptake by day. A mesocosm experiment with Tillandsia fasciculata (CAM) and Werauhia sanguinolenta (C-3) was combined with simulations using a non-steady-state oxygen isotope leaf water model. For both C-3 and CAM bromeliads, delta O-18(lw) became progressively depleted under saturating water vapour by day and night, although evaporative enrichment was restored in the C-3 W. sanguinolenta under low humidity by day. Source water in the overlapping leaf base 'tank' was also modified by evaporative delta O-18 exchanges. The results demonstrate how stable isotopes in leaf water provide insights for atmospheric water vapour exchanges for both C-3 and CAM systems.
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