Ozone sensitivity, growth and flower development in Phleum genotypes of different geographic origin in the Nordic countries

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Nine genotypes of Phleum pratense, with origins ranging from the southernmost part of Denmark to the Scandian mountains and the coast of the Barents sea, and three genotypes of Phleum alpinum, all from the boreal region of north Sweden, were exposed to four treatments: charcoal and purafil filtered air with or without an addition of 140 g m −3 ozone, and non-filtered air with or without an addition of 100 g m −3 ozone, in open-top chambers. Plants were also grown in the ambient air to be able to control the influence of the chamber climate. Filtration of the air did not significantly affect plant growth or flowering. In terms of growth reduction, P. alpinum was more sensitive to the elevated ozone concentration than P. pratense, but the effects of elevated ozone on P. pratense were also large and significant. The ozone sensitivity of P. pratense genotypes did not vary systematically with the geographical origin but covaried with the growth rate. The higher temperature in the open-top chambers had a positive effect on biomass production of genotypes from the sites with the highest summer temperatures, while it affected negatively growth and flowering in most of the genotypes from the sites with the lowest summer temperature. On average, the higher temperatures in the open-top chambers affected positively the average aboveground biomass production of the P. pratense genotypes, while the development of flowers was slightly negatively affected.