title: Weak coordination among petiole, leaf, vein, and gas-exchange traits across Australian angiosperm species and its possible implications.
abstract: Close coordination between leaf gas exchange and maximal hydraulic supply has been reported across diverse plant life forms. However, it has also been suggested that this relationship may become weak or break down completely within the angiosperms. We examined coordination between hydraulic, leaf vein, and gas-exchange traits across a diverse group of 35 evergreen Australian angiosperms, spanning a large range in leaf structure and habitat. Leaf-specific conductance was calculated from petiole vessel anatomy and was also measured directly using the rehydration technique. Leaf vein density (thought to be a determinant of gas exchange rate), maximal stomatal conductance, and net CO 2 assimilation rate were also measured for most species (n = 19-35). Vein density was not correlated with leaf-specific conductance (either calculated or measured), stomatal conductance, nor maximal net CO 2 assimilation, with r (2) values ranging from 0.00 to 0.11, P values from 0.909 to 0.102, and n values from 19 to 35 in all cases. Leaf-specific conductance calculated from petiole anatomy was weakly correlated with maximal stomatal conductance (r (2) = 0.16; P = 0.022; n = 32), whereas the direct measurement of leaf-specific conductance was weakly correlated with net maximal CO 2 assimilation (r (2) = 0.21; P = 0.005; n = 35). Calculated leaf-specific conductance, xylem ultrastructure, and leaf vein density do not appear to be reliable proxy traits for assessing differences in rates of gas exchange or growth across diverse sets of evergreen angiosperms.
authors.affiliation: Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia; Water Management Research Unit USDA-ARS Fort Collins Colorado 80526.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Gleason
authors.affiliation: Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia; Hawkesbury Institute for the Environment University of Western Sydney Richmond NSW 2753 Australia.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Blackman
authors.affiliation: Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia; CSIRO Agriculture LB 59 Narrabri NSW 2390 Australia.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Chang
authors.affiliation: Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia.
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Cook
authors.affiliation: Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia.
authors.forename: Claire A
authors.initials: CA
authors.lastname: Laws
authors.affiliation: Department of Biological Sciences Macquarie University North Ryde NSW 2109 Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Westoby
keywords: Angiosperms; CO2 assimilation; gas exchange; plant hydraulics; stomatal conductance; trait coordination
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