1. Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan / 2. Hokkaido DALTON, Sapporo 060-0808, Japan / 3. Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu-Tokyo 183-8509, Japan / 4. Hokkaido University Forests, Field Science Center for Northern Biosphere, Hokkaido University, Sapporo 060-0809, Japan / 5. Corresponding author () / Received April 24, 2007; accepted July 25, 2007; published online December 3, 2007
Summary
Water relations in woody species are intimately related to xylem hydraulic properties. High CO2 concentrations ([CO2]) generally decrease transpiration and stomatal conductance (gs), but there is little information about the effect of atmospheric [CO2] on xylem hydraulic properties. To determine the relationship between water flow and hydraulic structure at high [CO2], we investigated responses of sun and shade leaves of 4-year-old saplings of diffuse-porous Betula maximowicziana Regel and ring-porous Quercus mongolica Fisch. ex Ledeb. ssp. crispula (Blume) Menitsky grown on fertile brown forest soil or infertile volcanic ash soil and exposed to 500 µmol CO2 mol–1 for 3 years. Regardless of species and soil type, elevated [CO2] consistently decreased water flow (i.e., gs and leaf-specific hydraulic conductivity) and total vessel area of the petiole in sun leaves; however, it had no effect on
these parameters in shade leaves, perhaps because gs of shade leaves was already low. Changes in water flow at elevated [CO2] were associated with changes in petiole hydraulic properties.
Keywords:
cool-temperate northern Japan, free air CO2 enrichment (FACE), Hagen-Poiseuille law, hydraulic conductivity, petiole anatomy, stomatal conductance, vessel, water flow.
