Impact of elevated O3 and CO2 exposure on potato (Solanum tuberosum L. cv. Bintje) tuber macronutrients (N,P, K,Mg, Ca)

It was investigated whether exposure of elevated ozone (O₃) and carbon dioxide (CO₂) concentrations affected the macronutrient (N, P, K, Mg, Ca) concentrations in potato (Solanum tuberosum L.) tubers in three open-top chamber experiments from Sweden and Finland. The tuber concentrations of N, P, K and Mg correlated positively with O₃ exposure (although not significantly in the case of N and P) but the O₃ exposure had no effect on the tuber concentration of Ca. A likely mechanism behind the observed O₃ effects was suggested to be that the more progressed senescence of O₃ exposed plants was associated with a larger extent of reallocation of mobile nutrients from the haulm to the tubers. In addition, the uptake of macronutrients may have been less negatively affected by O₃ exposure than the assimilation of carbon. O₃ tended to reduce the total tuber contents of all investigated nutrients, which imply a reduced fertilizer need per unit field area. This was not associated with a decreased fertilizer need per tonnage of yield, as the tuber nutrient concentrations were increased by O₃ exposure. The increased CO₂ concentration did not significantly affect any of the investigated macronutrients in the present dataset but did generally prevent the O₃ induced increases in nutrient concentrations to be expressed (only significant in the case of N and Mg). The O₃ induced increase in tuber K concentration, may mediate earlier observed O₃ effects on potato tuber concentrations of citric and malic acids. To conclude, anticipated future (and even presently occurring) O₃ exposure has a negative impact on the total tuber contents of K and Ca and probably also on the total tuber contents of N, P and Mg. O₃ exposure causes increased tuber concentrations of N, P, K and Mg at an early harvest. The O₃ induced increase in tuber concentration tended to diminish by a CO₂ elevation.