Medeiros, Juliana S.Ward, Joy K.2017-06-272017-06-272013-08Medeiros, J. S. and Ward, J. K. (2013), Increasing atmospheric [CO2] from glacial to future concentrations affects drought tolerance via impacts on leaves, xylem and their integrated function. New Phytol, 199: 738–748. doi:10.1111/nph.12318https://hdl.handle.net/1808/24656This is the peer reviewed version of the following article: Medeiros, J. S. and Ward, J. K. (2013), Increasing atmospheric [CO2] from glacial to future concentrations affects drought tolerance via impacts on leaves, xylem and their integrated function. New Phytol, 199: 738–748. doi:10.1111/nph.12318, which has been published in final form at http://doi.org/10.1111/nph.12318. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Changes in atmospheric carbon dioxide concentration ([CO2]) affect plant carbon/water trade-offs, with implications for drought tolerance. Leaf-level studies often indicate that drought tolerance may increase with rising [CO2], but integrated leaf and xylem responses are not well understood in this respect. In addition, the influence of low [CO2] of the last glacial period on drought tolerance and xylem properties is not well understood. We investigated the interactive effects of a broad range of [CO2] and plant water potentials on leaf function, xylem structure and function and the integration of leaf and xylem function in Phaseolus vulgaris. Elevated [CO2] decreased vessel implosion strength, reduced conduit specific hydraulic conductance, and compromised leaf specific xylem hydraulic conductance under moderate drought. By contrast, at glacial [CO2], transpiration was maintained under moderate drought via greater conduit specific and leaf specific hydraulic conductance in association with increased vessel implosion strength. Our study involving the integration of leaf and xylem responses suggests that increasing [CO2] does not improve drought tolerance. We show that under glacial conditions changes in leaf and xylem properties could increase drought tolerance, while under future conditions greater productivity may only occur when higher water use can be accommodated.Drought toleranceElevated [CO2]Glacial [CO2]Leaf and xylem integrationXylem hydraulic conductanceArticle10.1111/nph.12318PMC3710516openAccess