Effects of elevated carbon dioxide and ozone on potato tuber quality in the European multiple-site experiment 'CHIP-project'

Potato (Solanum tuberosum L cv. Bintje) was exposed to ambient and elevated carbon dioxide (CO(2)), to ambient and elevated ozone (O(3)) and to elevated levels of both gases during two growing seasons, 1998 and 1999. Experiments in open-top chambers (OTC) were carried out in Finland, Sweden, Ireland, United Kingdom, Germany and Belgium and a FACE (Free Air Carbon dioxide Enrichment) experiment was carried out in Italy. In OTCs the plants were grown tinder ambient CO(2) concentrations or with 550 and 680 mul 1(-1) CO(2) alone or in combination with ambient or elevated 03 concentrations (target seasonal mean of 60 nl 1(-1) 8 h per day). In the FACE systems the plants were exposed to ambient or 550 mul 1(-1) CO(2). In the OTC experiments the reducing sugar content of potato tubers decreased significantly with increased concentration Of O(3). The starch content of potato tubers decreased, with negative impact on tuber quality, but the ascorbic acid concentration increased as a function of the AOT40 (The sum of the differences between hourly ozone concentration and 40 nl 1(-1) for each hour when the concentration exceeds 40 nl 1(-1) during a relevant growing season). However, simultaneous exposure to elevated CO(2) counteracted the ozone effect. With increase in the CO(2) exposure, glycoalkaloid and nitrate concentrations decreased yielding. improved quality, while the citric acid concentration decreased causing a higher risk for discoloration after cooking. The amount of dry matter and starch increased significantly in the FACE experiment.