EFFECTS OF OZONE ON THE GRAIN COMPOSITION OF SPRING WHEAT GROWN IN OPEN-TOP FIELD CHAMBERS

In a three-year study carried out at a rural site in Switzerland, spring wheat (Triticum aestivum L. cv. Albis) was exposed to different levels of ozone (O3) in open-top-field chambers from the two-leaf stage until harvest. Field plots in ambient air (AA) were used for comparison. Grain recovered from the different treatments was analyzed for minerals (Ca, Mg, K, P), starch, protein, amino acids and α-tocopherol, in order to investigate the effect of O3 on grain composition. Chamber-enclosure had small effects on some parameters (K, protein), but not on others (starch), as shown by the comparison of data from the AA and non-filtered-air treatment (NF). Differences between NF and charcoal-filtered air (CF) were very small. At O3 concentrations higher than in the NF treatment (O3-1 = 1·5 × NF and O3-2 = 2·5 × NF), mineral contents were higher than in the NF and CF treatments. Protein content was increased only in the O3-2 treatment. Starch contents decreased from about 63% in the CF treatment to 54% in the O3-2 tratment. No effect of O3 on the content of α-tocopherol and on the essential amino acid index of the protein was observed. It is concluded that compositional changes in wheat grain in response to O3 are minor, and that ambient O3 is not likely to cause important changes. © 1990.