Betula papyrifera trees were exposed to elevated concentrations of CO2 (1.4 × ambient), O3 (1.2 × ambient) or CO2 + O3 at the Aspen Free-air CO2 Enrichment Experiment. The treatment effects on leaf surface characteristics were studied after nine years of tree exposure. CO2 and O3 increased epidermal cell size and reduced epidermal cell density but leaf size was not altered. Stomatal density remained unaffected, but stomatal index increased under elevated CO2. Cuticular ridges and epicuticular wax crystallites were less evident under CO2 and CO2 + O3. The increase in amorphous deposits, particularly under CO2 + O3, was associated with the appearance of elongated plate crystallites in stomatal chambers. Increased proportions of alkyl esters resulted from increased esterification of fatty acids and alcohols under elevated CO2 + O3. The combination of elevated CO2 and O3 resulted in different responses than expected under exposure to CO2 or O3 alone.
Bibliographical noteFunding Information:
Aspen FACE is principally supported by the Office of Science (BER), U.S. Department of Energy, Grant No. DE-FG02-95ER62125 to Michigan Technological University, and Contract No. DE-AC02-98CH10886 to Brookhaven National Laboratory, the U.S. Forest Service Northern Global Change Program and Northern Research Station, Michigan Technological University, and Natural Resources Canada – Canadian Forest Service. This research was supported by the Emil Aaltonen Foundation and the Kone Foundation. We thank the support personnel of the Aspen FACE facility.
- Betula papyrifera
- Carbon dioxide
- Epicuticular wax
- Epidermal cell
- Leaf size