Xylem hydraulic characteristics of subtropical trees from contrasting habitats grown under identical environmental conditions |
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Authors: | C VANDER WILLIGEN H W SHERWIN & N W PAMMENTER |
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Institution: | School of Life and Environmental Sciences, George Campbell Building, University of Natal, Durban 4041, South Africa; Author for correspondence (fax +27 31 260 2029;e-mail;). |
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Abstract: | Five evergreen subtropical tree species growing under identical environmental conditions were investigated to establish which hydraulic properties are genotypically rigid and which show phenotypic plasticity. Maximum xylem-specific conductivity ( k s) correlated well with the anatomical characteristics (conduit diameter and density) for the four angiosperms Tecomaria capensis , Trichilia dregeana , Cinnamomum camphora and Barringtonia racemosa ; the anatomy of the gymnosperm Podocarpus latifolius was not assessed. Huber values (functional xylem cross-sectional area : leaf area) varied inversely with k s among species. Maximum leaf-specific conductivity was similar in the five unrelated species. Vulnerability of xylem to cavitation differed between species, as did the relationship between transpiration and water potential. Models of these parameters and isolated midday readings confirm that these trees operate at similar maximum leaf-specific conductivity ( k l) values. The data are consistent with the hypothesis that conductivity characteristics ( k l, k s) are influenced by environment, whereas vulnerability to cavitation is genetically determined. |
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Keywords: | hydraulic architecture hydraulic conductivity embolism cavitation vulnerability curve water relations transpiration xylem |
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