Environmental regulation of carbon isotope composition and crassulacean acid metabolism in three plant communities along a water availability gradient |
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Authors: | M Fernanda Ricalde José Luis Andrade Rafael Durán Juan Manuel Dupuy J Luis Simá Roberth Us-Santamaría Louis S Santiago |
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Institution: | 1. Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, A. C., Calle 43 # 130, Col. Chuburná de Hidalgo, 97200, Mérida, Yucatán, Mexico 2. Department of Botany and Plant Sciences, University of California, 2150 Batchelor Hall, Riverside, CA, 92521, USA 3. Facility for Isotope Ratio Mass Spectrometry (FIRMS), Center for Conservation Biology, University of California, Riverside, CA, 92521, USA
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Abstract: | Expression of crassulacean acid metabolism (CAM) is characterized by extreme variability within and between taxa and its sensitivity
to environmental variation. In this study, we determined seasonal fluctuations in CAM photosynthesis with measurements of
nocturnal tissue acidification and carbon isotopic composition (δ13C) of bulk tissue and extracted sugars in three plant communities along a precipitation gradient (500, 700, and 1,000 mm year−1) on the Yucatan Peninsula. We also related the degree of CAM to light habitat and relative abundance of species in the three
sites. For all species, the greatest tissue acid accumulation occurred during the rainy season. In the 500 mm site, tissue
acidification was greater for the species growing at 30% of daily total photon flux density (PFD) than species growing at
80% PFD. Whereas in the two wetter sites, the species growing at 80% total PFD had greater tissue acidification. All species
had values of bulk tissue δ13C less negative than −20‰, indicating strong CAM activity. The bulk tissue δ13C values in plants from the 500 mm site were 2‰ less negative than in plants from the wetter sites, and the only species growing
in the three communities, Acanthocereus tetragonus (Cactaceae), showed a significant negative relationship between both bulk tissue and sugar δ13C values and annual rainfall, consistent with greater CO2 assimilation through the CAM pathway with decreasing water availability. Overall, variation in the use of CAM photosynthesis
was related to water and light availability and CAM appeared to be more ecologically important in the tropical dry forests
than in the coastal dune. |
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