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

Nine genotypes of Phleum pratense, with origins ranging from the southernmo st part of Denmark to the Scandian mountains and the coast of the Parents s ea, and three genotypes of Phleum alpinum, all from the boreal region of no rth 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. Pla nts 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 mor e sensitive to the elevated ozone concentration than P. pratense, but the e ffects of elevated ozone on P. pratense were also large and significant. Th e ozone sensitivity of P. pratense genotypes did not vary systematically wi th the geographical origin but covaried with the growth rate. The higher te mperature in the open-top chambers had a positive effect on biomass product ion 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 temper atures 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. (C) 1999 Elsevier Science B.V. Al l rights reserved.