Studies on the Efects of Low Levels of Sulphur Dioxide on the Growth of Lolium Perenne L.

Summary Lolium perenne L. cv. S23 was grown in Perspex chambers situated out of doors and ventilated with clean air or controlled levels of sulphur dioxide (SO2). Fumigations were carried out with [SO2] ranging from 43 to 423 μg m−3 for periods up to 194 days under both summer and winter conditions. Concentrations as low as 43 μg m−3 for 173 days in winter and 106 μg m−3 for 194 days in summer could produce reductions in shoot dry wt but, in some experiments, similar or higher concentrations had no effect on growth. This difficulty in obtaining a clear dose/response relationship is possibly due to an interaction of environmental factors with the effects of the pollutants. In some of the experiments, growth was reduced in the absence of any detectable symptoms whereas, in other cases, the fumigated plants became chlorotic. There was some evidence for chronic SO2 injury being more severe on young plants. SO2 acted primarily through a depression in net assimilation rate. No clear correlation was found between either chlorophyll content or total sulphur content of the fumigated plants and a reduction in any of the growth parameters investigated. The results are discussed in relation to those of other workers and their relevance to conditions in the field in the United Kingdom.