Effects of Ozone on Growth of Seven Grass and One Clover Species

Seven species of grass and one of red clover were grown at different ozone (O3) concentrations for about five weeks in growth chambers located in a greenhouse. At an O3 concentration of 55 compared with 10 nmol mol−1 during 7 h day−1 the shoot dry weight decreased by 45% in Phleum pratense, 28% in Dactylis glomerata and Poa pratensis, 23% in Festuca rubra and 16% in Festuca pratensis, while the effects on Agrostis tenuis were not significant. No effect was found at 25 compared with 10 nmol mol−1O3. Visible O3 injury was observed in all six species at 55 nmol mol−1 and this effect was generally well correlated with the effect on the dry weights. In another experiment no effect was found with O3 concentrations of up to 62 nmol mol−1 on Lolium perénne, while the dry weight in Trifolium pratense decreased by 30% at 59 compared with that at 6 nmol mol−1.