Leaf size and surface characteristics of Betula papyrifera exposed to elevated CO_2 and O_3

摘要

Betula papyrifera trees were exposed to elevated concentrations of CO_2 (1.4 × ambient), O_3 (1.2 × ambient) or CO_2 + O_3 at the Aspen Free-air CO_2 Enrichment Experiment. The treatment effects on leaf surface characteristics were studied after nine years of tree exposure. CO_2 and O_3 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 CO_2. Cuticular ridges and epicuticular wax crystallites were less evident under CO_2 and CO_2 + O_3. The increase in amorphous deposits, particularly under CO_2 + O_3, 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 CO_2 + O_3. The combination of elevated CO_2 and O_3 resulted in different responses than expected under exposure to CO_2 or O_3 alone.