PHASEOLUS-VULGARIS AND OZONE - RESULTS FROM OPEN-TOP CHAMBER EXPERIMENTS IN FRANCE AND ENGLAND

The response of Phaseolus vulgaris cv. 'Lit' to O3 was investigated in open-top chamber (OTC) experiments at Sutton Bonington in the English East Midlands, and Pau in the south-west of France. At both sites, the crop was exposed in OTCs ventilated with charcoal-filtered air (Pau-CF and SB-CF treatments), non-filtered air (Pau-NF and SB-NF) or non-filtered air with added O3 (Pau-NF20 and SB-NFL, -NFM, -NFH). In the Pau experiment, O3 was added for 7 h day-1 and 7 days week 1, whereas in the Sutton Bonington experiment O3 additions were for 7 h day-1, and 3-4 days week-1. The seasonal 7-h mean O3 concentrations were 8, 39 and 58 nl l-1 in the Pau-CF, -NF and -NF20 treatments, respectively, and 8, 21, 27, 33 and 38 nl l-1 in the SB-CF, -NF, -NFL, -NFM and -NFH treatments, respectively. Bronze stippling, characteristic of chronic O3 stress, appeared 21 days after emergence (DAE) in the Pau-NF20 treatment, and 60 DAE in the SB-NFH treatment. At the green harvest (61 and 66 DAE at Pau and Sutton Bonington, respectively) there was a 41% reduction in plant dry weight in the Pau-NF20 treatment (compared with the Pau-CF treatment) whereas there were no significant O3 effects on dry weight in any of the Sutton Bonington treatments. By the dry harvest, the percentage effect of O3 on seed yield was linearly related to the seasonal 7-h mean O3 concentration. The results from both experiments fitted into the same relationship even though there were differences in the O3 exposure regime, physical and pollution climates and soil characteristics at Sutton Bonington and Pau.