Effects of Ozone in Ambient Air on Growth, Yield and Physiological Parameters of Spring Wheat

A spring wheat cultivar (Triticum aestivum, cv Albis) was grown near Bern (Switzerland) in open-top chambers and open-field plots and exposed daily to different ozone concentrations in ambient air. Seasonal 8-hr/day (0900–1700) ozone concentrations were 0.020 ppm in charcoal-filtered air, 0.035 ppm in nonfiltered air, 0.103 ppm in ozone-enriched air and 0.040 ppm in ambient air. Growth, yield and various physiological parameters were studied. Grain yield was the most ozone-sensitive parameter, much more sensitive than straw yield or growth. In filtered air, grain yield was 9% higher than in nonfiltered air, and 127% higher than in ozone-enriched air. Differences in grain yield appeared to be linked to direct effects of ozone on CO2-fixation of flag leaves. Measurements of chlorophyll content and ethylene production revealed that stress from elevated ozone concentrations can affect processes associated with leaf senescence.