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Leaf water δ18O reflects water vapour exchange and uptake by C3 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
Source :
Functional Plant Biology; 2021, Vol. 48 Issue 7, p732-742, 11p
Publication Year :
2021

Abstract

The distributions of CAM and C<subscript>3</subscript> epiphytic bromeliads across an altitudinal gradient in western Panama were identified from carbon isotope (δ<superscript>13</superscript>C) signals, and epiphyte water balance was investigated via oxygen isotopes (δ<superscript>18</superscript>O) across wet and dry seasons. There were significant seasonal differences in leaf water (δ<superscript>18</superscript>O<subscript>lw</subscript>), precipitation, stored 'tank' water and water vapour. Values of δ<superscript>18</superscript>O<subscript>lw</subscript> were evaporatively enriched at low altitude in the dry season for the C<subscript>3</subscript> epiphytes, associated with low relative humidity (RH) during the day. Crassulacean acid metabolism (CAM) δ<superscript>18</superscript>O<subscript>lw</subscript> values were relatively depleted, consistent with water vapour uptake during gas exchange under high RH at night. At high altitude, cloudforest locations, C<subscript>3</subscript> δ<superscript>18</superscript>O<subscript>lw</subscript> also reflected water vapour uptake by day. A mesocosm experiment with Tillandsia fasciculata (CAM) and Werauhia sanguinolenta (C<subscript>3</subscript>) was combined with simulations using a non-steady-state oxygen isotope leaf water model. For both C<subscript>3</subscript> and CAM bromeliads, δ<superscript>18</superscript>O<subscript>lw</subscript> became progressively depleted under saturating water vapour by day and night, although evaporative enrichment was restored in the C<subscript>3</subscript> W. sanguinolenta under low humidity by day. Source water in the overlapping leaf base 'tank' was also modified by evaporative δ<superscript>18</superscript>O exchanges. The results demonstrate how stable isotopes in leaf water provide insights for atmospheric water vapour exchanges for both C<subscript>3</subscript> and CAM systems. The paper defines the niche segregation of C<subscript>3</subscript> and CAM photosynthetic pathways for epiphytic bromeliads along an altitudinal gradient in Panama. Measurement of the leaf water oxygen (<superscript>18</superscript>O) stable isotope composition supports transpiration by day or night, since under high humidity water vapour influx resets the leaf water <superscript>18</superscript>O signal. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
14454408
Volume :
48
Issue :
7
Database :
Complementary Index
Journal :
Functional Plant Biology
Publication Type :
Academic Journal
Accession number :
150747450
Full Text :
https://doi.org/10.1071/FP21087