Responses of foliar gas exchange to long-term elevated CO2 concentrations in mature loblolly pine trees
- 1 June 1995
- journal article
- research article
- Published by Oxford University Press (OUP) in Tree Physiology
- Vol. 15 (6) , 351-359
- https://doi.org/10.1093/treephys/15.6.351
Abstract
Branches of field-grown mature loblolly pine (Pinus taeda L.) trees were exposed for 2 years (1992 and 1993) to ambient or elevated CO2 concentrations (ambient + 165 μmol mol−1 or ambient + 330 μmol mol−1 CO2). Exposure to elevated CO2 concentrations enhanced rates of net photosynthesis (Pn) by 53–111% compared to Pn of foliage exposed to ambient CO2. At the same CO2 measurement concentration, the ratio of intercellular to atmospheric CO2 concentration (Ci/Ca) and stomatal conductance to water vapor did not differ among foliage grown in an ambient or enriched CO2 concentration. Analysis of the relationship between Pn and Ci indicated no significant change in carboxylation efficiency of ribulose-1,5-bisphosphate carboxylase/oxygenase during growth in elevated CO2 concentrations. Based on estimates derived from Pn/Ci curves, there were no apparent treatment differences in dark respiration, CO2 compensation point or Pn at the mean Ci. In 1992, foliage in the three CO2 treatments yielded similar estimates of CO2-saturated Pn (Pmax), whereas in 1993, estimates of Pmax were higher for branches grown in elevated CO2 than in ambient CO2. We conclude that field-grown loblolly pine trees do not exhibit downward acclimation of leaf-level photosynthesis in their long-term response to elevated CO2 concentrations.Keywords
This publication has 0 references indexed in Scilit: