Oecologia

, Volume 143, Issue 4, pp 652–660

Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2

Authors

  • Penny J. Tricker
    • School of Biological SciencesUniversity of Southampton
  • Harriet Trewin
    • School of Biological SciencesUniversity of Southampton
  • Olevi Kull
    • Institute of Botany and Ecology
  • Graham J. J. Clarkson
    • School of Biological SciencesUniversity of Southampton
  • Eve Eensalu
    • Institute of Botany and Ecology
  • Matthew J. Tallis
    • School of Biological SciencesUniversity of Southampton
  • Alessio Colella
    • Department of Environmental SciencesII University of Naples
  • C. Patrick Doncaster
    • School of Biological SciencesUniversity of Southampton
  • Maurizio Sabatti
    • Department of Forest Environment and ResourcesUniversita degli Studi della Tuscia
    • School of Biological SciencesUniversity of Southampton
Global Change Ecology

DOI: 10.1007/s00442-005-0025-4

Cite this article as:
Tricker, P.J., Trewin, H., Kull, O. et al. Oecologia (2005) 143: 652. doi:10.1007/s00442-005-0025-4

Abstract

Using a free-air CO2 enrichment (FACE) experiment, poplar trees (Populus × euramericana clone I214) were exposed to either ambient or elevated [CO2] from planting, for a 5-year period during canopy development, closure, coppice and re-growth. In each year, measurements were taken of stomatal density (SD, number mm−2) and stomatal index (SI, the proportion of epidermal cells forming stomata). In year 5, measurements were also taken of leaf stomatal conductance (g s, μmol m−2 s−1), photosynthetic CO2 fixation (A, mmol m−2 s−1), instantaneous water-use efficiency (A/E) and the ratio of intercellular to atmospheric CO2 (Ci:Ca). Elevated [CO2] caused reductions in SI in the first year, and in SD in the first 2 years, when the canopy was largely open. In following years, when the canopy had closed, elevated [CO2] had no detectable effects on stomatal numbers or index. In contrast, even after 5 years of exposure to elevated [CO2], g s was reduced, A/E was stimulated, and Ci:Ca was reduced relative to ambient [CO2]. These outcomes from the long-term realistic field conditions of this forest FACE experiment suggest that stomatal numbers (SD and SI) had no role in determining the improved instantaneous leaf-level efficiency of water use under elevated [CO2]. We propose that altered cuticular development during canopy closure may partially explain the changing response of stomata to elevated [CO2], although the mechanism for this remains obscure.

Keywords

Populus × euramericana Stomatal numbers Stomatal conductance POPFACE

Copyright information

© Springer-Verlag 2005