Stomatal responses of strawberry heaves to moderate ozone

Strawberry plants (Fragaria x ananassa Duch.) of cvs. 'Elsanta' and 'Korona ' were fumigated for eight hours five days a week with 75 ppb ozone for eig ht days at an atmospheric CO2 concentration of 360 or 720 ppm, or with 65 p pb ozone for three months at 360 ppm CO2 The short term ozone application a t 360 ppm CO2 did not affect leaf gas exchange, but at 720 ppm, stomatal co nductance was significantly reduced by ozone in both cultivars. Long term e xposure to 65 ppb ozone at an atmospheric CO2 level of 360 ppm caused an in crease in stomatal density, stomatal conductance, and intercellular CO2 con centration in cv. 'Elsanta' leaves, which emerged under the ozone exposure. In cv. 'Korona', the long term ozone application did not affect stomatal d ensity and leaf gas exchange. The results suggest that ozone can directly a ffect stomatal aperture in strawberry. The stomatal responses of cvs. 'Elsa nta' and 'Korona' to ozone may be regarded as adaptations to maintain leaf net photosynthesis rates similar to those of untreated control leaves.