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First published online February 11, 2009; 10.1104/pp.108.129015 Plant Physiology 149:1992-1999 (2009) © 2009 American Society of Plant Biologists
Water Relations of Chusquea ramosissima and Merostachys claussenii in Iguazu National Park, Argentina1The Arnold Arboretum of Harvard University, Cambridge, Massachusetts 02130 (S.S.); Biological Laboratories, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138 (N.M.H.); Laboratorio de Ecología Funcional, Consejo Nacional de Investigaciones Científicas y Técnicas, Departamento de Ecología Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C1428EHA Buenos Aires, Argentina (L.M., G.G.); and Instituto de Pesquisa Ambiental da Amazônia, Canarana MT 78640–000, Brazil (G.K.C.)
Bamboos are prominent components of many tropical ecosystems, yet little is known about the physiological mechanisms utilized by these gigantic forest grasses. Here, we present data on the water transport properties of Chusquea ramosissima and Merostachys claussenii, monocarpic bamboo grasses native to the subtropical Atlantic forests of Argentina. C. ramosissima and M. claussenii differed in their growth form and exhibited contrasting strategies of water transport. Maximum xylem hydraulic conductivity of C. ramosissima culms was 2-fold higher than that of M. claussenii. C. ramosissima cavitated at relatively high water potentials (50% loss of conductivity at
1 This work was supported by The Arnold Arboretum and The David Rockefeller Center for Latin American Studies, both of Harvard University, and The Andrew W. Mellon Foundation. 2 Present address: The Institute for Regional Conservation, 22601 SW 152nd Ave., Miami, FL 33170. 3 Present address: Consejo Nacional de Investigaciones Científicas y Técnicas, C1428EHA Buenos Aires, Argentina. The author responsible for the distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Sonali Saha (saha{at}regionalconservation.org). www.plantphysiol.org/cgi/doi/10.1104/pp.108.129015 * Corresponding author; e-mail saha{at}regionalconservation.org. Received September 1, 2008; accepted February 4, 2009; published February 11, 2009. Related articles in Plant Physiol.:
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1 MPa), whereas M. claussenii was more drought tolerant (50% loss at 
3 MPa). Both species exhibited significant loss of hydraulic conductivity during the day, which was reversed overnight due to the generation of root pressure. The photosynthetic capacities of both bamboo species, estimated based on electron transport rates, were moderate, reflecting both the large amount of leaf area supported by culms and diurnal loss of hydraulic conductivity due to cavitation. Leaf hydraulic conductance was also relatively low for both species, congruent with their modest photosynthetic capacities. Within its native range, C. ramosissima is highly invasive due to its ability to colonize and persist in both forest gaps and land cleared for agriculture. We propose that a highly vulnerable vasculature, coupled with diurnal root pressure and an allometry that allows substantial leaf area to be supported on relatively slender culms, are key traits contributing to the ecological success of C. ramosissima.