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- Title
Leaf water δ<sup>18</sup>O reflects water vapour exchange and uptake by C<sub>3</sub> and CAM epiphytic bromeliads in Panama.
- Authors
Mejia-Chang, Monica; Reyes-Garcia, Casandra; Seibt, Ulli; Royles, Jessica; Meyer, Moritz T.; Jones, Glyn D.; Winter, Klaus; Arnedo, Miquel; Griffiths, Howard
- Abstract
The distributions of CAM and C3 epiphytic bromeliads across an altitudinal gradient in western Panama were identified from carbon isotope (δ13C) signals, and epiphyte water balance was investigated via oxygen isotopes (δ18O) across wet and dry seasons. There were significant seasonal differences in leaf water (δ18Olw), precipitation, stored 'tank' water and water vapour. Values of δ18Olw were evaporatively enriched at low altitude in the dry season for the C3 epiphytes, associated with low relative humidity (RH) during the day. Crassulacean acid metabolism (CAM) δ18Olw values were relatively depleted, consistent with water vapour uptake during gas exchange under high RH at night. At high altitude, cloudforest locations, C3 δ18Olw also reflected water vapour uptake by day. A mesocosm experiment with Tillandsia fasciculata (CAM) and Werauhia sanguinolenta (C3) was combined with simulations using a non-steady-state oxygen isotope leaf water model. For both C3 and CAM bromeliads, δ18Olw became progressively depleted under saturating water vapour by day and night, although evaporative enrichment was restored in the C3 W. sanguinolenta under low humidity by day. Source water in the overlapping leaf base 'tank' was also modified by evaporative δ18O exchanges. The results demonstrate how stable isotopes in leaf water provide insights for atmospheric water vapour exchanges for both C3 and CAM systems. The paper defines the niche segregation of C3 and CAM photosynthetic pathways for epiphytic bromeliads along an altitudinal gradient in Panama. Measurement of the leaf water oxygen (18O) stable isotope composition supports transpiration by day or night, since under high humidity water vapour influx resets the leaf water 18O signal.
- Subjects
PANAMA (Panama); WATER vapor; BROMELIACEAE; ATMOSPHERIC water vapor; CRASSULACEAN acid metabolism; OXYGEN isotopes; LEAF physiology; STABLE isotopes; PLANT transpiration
- Publication
Functional Plant Biology, 2021, Vol 48, Issue 7, p732
- ISSN
1445-4408
- Publication type
Article
- DOI
10.1071/FP21087