title: Xylem traits mediate a trade-off between resistance to freeze-thaw-induced embolism and photosynthetic capacity in overwintering evergreens.
abstract: Hydraulic traits were studied in temperate, woody evergreens in a high-elevation heath community to test for trade-offs between the delivery of water to canopies at rates sufficient to sustain photosynthesis and protection against disruption to vascular transport caused by freeze-thaw-induced embolism. Freeze-thaw-induced loss in hydraulic conductivity was studied in relation to xylem anatomy, leaf- and sapwood-specific hydraulic conductivity and gas exchange characteristics of leaves. We found evidence that a trade-off between xylem transport capacity and safety from freeze-thaw-induced embolism affects photosynthetic activity in overwintering evergreens. The mean hydraulically weighted xylem vessel diameter and sapwood-specific conductivity correlated with susceptibility to freeze-thaw-induced embolism. There was also a strong correlation of hydraulic supply and demand across species; interspecific differences in stomatal conductance and CO(2) assimilation rates were correlated linearly with sapwood- and leaf-specific hydraulic conductivity. Xylem vessel anatomy mediated an apparent trade-off between resistance to freeze-thaw-induced embolism and hydraulic and photosynthetic capacity during the winter. These results point to a new role for xylem functional traits in determining the degree to which species can maintain photosynthetic carbon gain despite freezing events and cold winter temperatures.
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Brendan
authors.initials: B
authors.lastname: Choat
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Danielle E
authors.initials: DE
authors.lastname: Medek
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Stuart
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA 90095-1606, USA.
authors.forename: Jessica
authors.initials: J
authors.lastname: Pasquet-Kok
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: John J G
authors.initials: JJG
authors.lastname: Egerton
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Hooman
authors.initials: H
authors.lastname: Salari
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA 90095-1606, USA.
authors.forename: Lawren
authors.initials: L
authors.lastname: Sack
authors.affiliation: Plant Science Division, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia.
authors.forename: Marilyn C
authors.initials: MC
authors.lastname: Ball
mesh_terms: D000222:Adaptation, Physiological; D001315:Australia; D001692:Biological Transport / Q000502:physiology; D003080:Cold Temperature; D006358:Hot Temperature; D019684:Magnoliopsida / Q000033:anatomy & histology / Q000502:physiology; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D018547:Plant Stems / Q000502:physiology; D054046:Plant Stomata / Q000502:physiology; D018526:Plant Transpiration; D012621:Seasons; D052584:Xylem / Q000033:anatomy & histology / Q000502:physiology*