title: Hydraulic architecture and photoinhibition influence spatial distribution of the arborescent palm Euterpe edulis in subtropical forests.
abstract: Physiological characteristics of saplings can be considered one of the most basic constraints on species distribution. The shade-tolerant arborescent palm Euterpe edulis Mart. is endemic to the Atlantic Forest of Argentina, Brazil and Paraguay. At a local scale, saplings of this species growing in native forests are absent in gaps. We tested the hypothesis whether sensitivity to photoinhibition or hydraulic architecture constrains the distribution of E. edulis saplings in sun-exposed forest environments. Using shade houses and field studies, we evaluated growth, survival, hydraulic traits and the susceptibility of Photosystem II to photoinhibition in E. edulis saplings under different growth irradiances. Survival rates in exposed sites in the field were very low (a median of 7%). All saplings exhibited photoinhibition when exposed to high radiation levels, but acclimation to a high radiation environment increased the rate of recovery. Petiole hydraulic conductivity was similar across treatments regardless of whether it was expressed per petiole cross-sectional area or per leaf area. At the plant level, investment in conductive tissues relative to leaf area (Huber values) increased with increasing irradiance. Under high irradiance conditions, plants experienced leaf water potentials close to the turgor-loss point, and leaf hydraulic conductance decreased by 79% relative to its maximum value. Euterpe edulis saplings were able to adjust their photosynthetic traits to different irradiance conditions, whereas hydraulic characteristics at the leaf level did not change across irradiance treatments. Our results indicate that uncoupling between water demand and supply to leaves apparently associated with high resistances to water flow at leaf insertion points, in addition to small stems with low water storage capacity, weak stomatal control and high vulnerability of leaves to hydraulic dysfunction, are the main ecophysiological constraints that prevent the growth and survival of E. edulis saplings in gaps in the native forest where native lianas and bamboos show aggressive growth.
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina Laboratorio de Ecología Funcional, Dept Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Present address: IBS-Instituto de Biología Subtropical, Universidad Nacional de Misiones, Bertoni 85, 3370 Puerto Iguazú, Misiones, Argentina genoveva.gatti@conicet.gov.ar.
authors.forename: M Genoveva
authors.initials: MG
authors.lastname: Gatti
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina Laboratorio de Ecología Funcional, Dept Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Present address: IBS-Instituto de Biología Subtropical, Universidad Nacional de Misiones, Bertoni 85, 3370 Puerto Iguazú, Misiones, Argentina.
authors.forename: Paula I
authors.initials: PI
authors.lastname: Campanello
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina Laboratorio de Ecología Funcional, Dept Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Present address: IBS-Instituto de Biología Subtropical, Universidad Nacional de Misiones, Bertoni 85, 3370 Puerto Iguazú, Misiones, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Villagra
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina Laboratorio de Ecología Funcional, Dept Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Present address: Instituto de Ecología Regional (IER), Universidad Nacional de Tucumán, CC 34, 4107 Yerba Buena, Tucumán, Argentina.
authors.forename: Lía
authors.initials: L
authors.lastname: Montti
authors.affiliation: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina Laboratorio de Ecología Funcional, Dept Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina Department of Biology, University of Miami, PO Box 249118, Coral Gables, FL 33124, USA.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Goldstein
mesh_terms: D000064:Acclimatization; D065748:Euterpe / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects; D065928:Forests; D008027:Light; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D018547:Plant Stems / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000502:physiology*; D036226:Seedlings / Q000254:growth & development / Q000502:physiology / Q000528:radiation effects; D014197:Trees; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water
keywords: gap; hydraulic conductivity; leaf hydraulic conductance; leaf water potential; semideciduous Atlantic Forest; understory