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Title: Weak coordination among petiole, leaf, vein, and gas-exchange traits across 41 Australian angiosperm species and its possible implications

item Gleason, Sean
item BLACKMAN, CHRIS - University Of Western Australia
item CHANG, YVONNE - Macquarie University
item COOK, ALICIA - Macquarie University
item LAWS, CLAIRE - Macquarie University
item WESTOBY, MARK - Macquarie University

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: 7/8/2016
Citation: Gleason, S.M., Blackman, C.J., Chang, Y., Cook, A., Laws, C., Westoby, M. 2016. Weak coordination among petiole, leaf, vein, and gas-exchange traits across 41 Australian angiosperm species and its possible implications. Ecology and Evolution. Ecol Evol.2016 Jan; 6(1):267-278.

Interpretive Summary: Quantifying the relationship between water transport through plants and rates of photosynthesis are important for many process-based growth models. Such models are presently being used to predict plant growth and growth response to changes in climate (e.g., precipitation and temperature). A proportional relationship between water transport (obtained from anatomical measurements) and photosynthesis is most often assumed. We tested this assumption across 44 Australian angiosperm species and found very little support for this assumption. Our data suggests that careful consideration should be given before using anatomic data (e.g., vessel dimensions, estimated rates of conductance, vein density) as proxy measurements for rates of stomatal conductance, CO2 assimilation, or growth.

Technical Abstract: Background and Aims Close coordination between leaf gas exchange and maximal hydraulic supply has been reported across diverse plant life-forms. However, recent reports suggest that this relationship may become weak or break down completely within the angiosperms. Methods To examine this possibility we estimated maximum petiole conductance across 41 Australian angiosperms spanning a large range in leaf structure and habitat. We also measured leaf vein characteristics thought to be determinants of gas exchange rates (vein density and xylem-specific conductance of veins) across these same species. Key Results Estimated conductance of leaf petioles was correlated with leaf size (r2 = 0.84; P < 0.001), as might be expected. Petiole conductance per leaf area (leaf-specific conductance) was only weakly correlated with maximum rates of stomatal conductance per area (r2 = 0.16; P = 0.022) and unrelated to rates of CO2 assimilation. Although vein density was not correlated with rates of stomatal conductance nor CO2 assimilation, the estimated xylem-specific conductance of veins was weakly correlated with stomatal conductance (r2 = 27; P = 0.002). Conclusion We strongly caution against using calculated leaf-specific conductance, xylem ultrastructure, or leaf vein density as proxy-traits for assessing differences in rates of gas exchange or growth across angiosperms.