Growth of Perennial Ryegrass (Lolium perenne L.) Exposed to a Low Concentration of Sulphur Dioxide

The influence of a low concentration of SO₂ on the growth andsulphur status of perennial ryegrass (Lolium perenne L.) cv.S23 was examined in a system of specially designed growth chambers.For plants grown without additions of sulphate to the soil,erposure to ifitered air containing 50 µg m^–3 SO₂alleviated sulphur deficiency that developed during a sequenceof successive harvests, and gave increased yield. The plantshad higher contents of organic and inorganic sulphur than thosegrown with neither sulphate nor SO₂. Plants grown with addedsulphate showed no signs of sulphur deficiency and althoughexposure to SO₂ increased their sulphur content it had no effecton yield. The coefficient of transpiration (g water transpiredg^–1 dry wt. of shoots) was reduced when plants which otherwisehad an inadequate supply of sulphur were exposed to SO₂; forplants with adequate supplies of sulphate, it was similar whetherthey were grown with or without the addition of SO₂ to the air.The results are discussed in relation to other known reactionsof plants to SO₂.