Potato tuber sugars, starch and organic acids in relation to ozone exposure

Data from two Swedish and one Finnish open-top chamber experiments were combined to investigate effects of ozone exposure on potato (Solanum tuberosum L.) tuber content of starch, sucrose, fructose, glucose, malic, citric and ascorbic acids. The glucose, fructose and malic acid concentrations showed strong negative correlations with ozone exposure, while citric acid, consistently increased with ozone exposure. No ozone effects could be demonstrated on starch, sucrose or ascorbic acid concentrations. It is discussed to what extent the changes found in potato tuber composition can be explained in terms of ozone effects on tuber maturity. Ozone exposure was expressed as the accumulated exposure over a cut-off concentration of 40 nmol mol−1(AOT40) and as the accumulated uptake of ozone over an ozone uptake rate threshold of 7 nmol m−2s−1(CUO 7). The difference in ability of the exposure indices to explain observed effects was small.