Tropospheric ozone decreases biomass production in radish plants (Raphanus sativus) grown in rural south-west Sweden

Potted plants of radish (Raphanus sativus L., cv. Cherry Belle) were grown in the ambient air for 5 weeks, with or without the application of a soil drench of the anti-ozonant ethylenediurea (EDU). The 24-h mean ozone concentration during the experimental period was 31 nl l(-1). Towards the end of the experiment two ozone episodes, with maximum concentrations around 70 and 115 nl l(-1), occurred. No visible injury that could be attributed to ozone was observed on any of the plants. Shoot and hypocotyl biomass were significantly lower in the non-EDU-treated plants than in the EDU-treated plants. The non-EDU-treated plants had a 32% lower hypocotyl biomass and a 22% lower shoot biomass. The shoot:hypocotyl ratio of the non-EDU-treated plants was higher than that of the EDU-treated plants, although the difference was not statistically significant. EDU treatment increased the leaf area and decreased the chlorophyll content of the leaves. These differences were, however, not statistically significant. It is suggested that the ambient rural ozone climate in southern Sweden has the potential to decrease biomass production in Cherry Belle radishes in the absence of visible injury.