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The leaf water uptake role in the water economy of Amazonian tropical trees.

Gina Knust Cardinot, IPAM/UFRJ, cardinot@ipam.org.br (Presenting)
Leonel Sternberg, University of Miami, leo@bio.miami.edu
Marcelo Zacarias Moreira, CENA/USP, mmoreira@cena.usp.br
Daniel Curtis Nepstad, WHRC/IPAM, dnepstad@whrc.org

Early studies have shown the importance of dew absorption by leaves in regions where fog is an important component. However, the importance of water uptake by leaves of trees in tropical forests has not been previously considered. We hypothesize here that leaf water absorption in tropical trees might be responsible for the drought tolerance exhibited by Amazonian forest trees, allowing them to maintain physiological function despite the marked seasonality in Eastern Amazon rainfall. Application of deuterium (deltaD) labeled water and leaf water potential (Y) measurements were carried out in three common primary forest tree species at Tapajós National Forest (Pará State-Brazil): Coussarea racemosa, Miconia egensis and Escheweilera pedicellata to test whether their leaves or stems absorb water directly. Two leaf irrigation treatments were carried out: leaves were sprayed with deuterated water and branches were exposed to deuterated water with a moist cotton band about 1m from the branch tip. After five days of the irrigation treatment Coussarea and Escheweilera showed significant response to the spray treatment increasing predawn and/or midday leaf water potential as well as on their deltaD abundance. Changes in the Miconia Y although in the right direction were not significant. The leaf water deltaD abundance in the sprayed leaves were significantly above background for all three species and followed the water potential response with species having the greatest Y response also having the greatest deltaD abundance. These results confirm the role of water absorption by leaves in the recovery of water-stressed plants.

Science Theme:  HY (Hydrometeorology)

Session:  2A: Hydrological and Meteorological Processes

Presentation Type:  Oral

Abstract ID: 64

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