Lolium perenne L. was grown in a sealed glass chamber force-ventilated with ambient SO2-polluted air and the yield compared with that of control plants grown in a second chamber receiving filtered air free of SO2 and suspended participates. Whole plant dry weight of L. perenne cv. S23 grown either on a nutrient-rich sand culture or an unfertilized field soil was depressed by up to 36% in polluted air containing mean SO2 concentrations of less than 100 μg−3 in. When detailed growth analyses of S23 L. perenne in unfiltered air and of a clone of wild L. perenne previously reported to be resistant to SO2 pollution were compared, there were distinct differences between the two strains in response to SO2-polluted air but both were less productive in the latter treatment.
Sulphur dioxide was strongly implicated as the factor responsible for the reduced dry-matter production of plants raised in polluted air but there was a poor positive correlation between loss of yield and long term mean SO2 concentration within the unfiltered air chamber. The results are discussed with regard to probable mechanisms of growth inhibition and the possibility that experimental conditions cither enhanced or confounded the effect of SO2 pollution on plant growth.