Ozone-induced ethylene release from leaf surfaces

Ozone-induced stress ethylene emissions from the adaxial and abaxial leaf surfaces of four plant species ( Glycine max [L.] Merr. cv. Dare, Lycopersicon esculentum Mill cv. Roma VF, Eucalyptus globulus Labill. and Hedera helix L.) were studied to determine if the stress ethylene diffused through the stomata or cuticle. In plants not exposed to ozone, basal ethylene was detected above both the adaxial and abaxial leaf surfaces of all the plant species examined, indicating that some ethylene can diffuse across the leaf cuticle. Ozone induced stress ethylene production in all species examined. Significant ozone-induced ethylene concentrations were detected above both surfaces of amphistomatous soybean ( Glycine) and tomato ( Lycopersicon) leaves. In contrast, ozone-induced ethylene production was associated only with the leaf surface (abaxial) that contained stomata for hypostomatous blue gum eucalyptus and English ivy ( Hedera) leaves; the leaf surface (adaxial) of the eucalyptus and ivy leaves which did not contain stomata did not release significant amounts of stress ethylene. These data indicate that ozone-induced stress ethylene primarily diffuses from the leaf via the stomata.