Studies on the tolerance to SO2 of grass populations in polluted areas

SUMMARY Grass populations were collected from two sites, Philips Park and Rainham, with different pollution characteristics. They were screened for acute and chronic air pollution injury caused by nitrogen dioxide (NO2) and by sulphur dioxide(SO2) in combination with NO2 in comparison with bred cultivars of the same species grown at a clean air site. No evidence of tolerance of acute NO2 or NO2/SO2, injury was found at Philips Park. A Dactylis glomerata L. population from Rainham showed tolerance to both types of injury. There was also some evidence to suggest that there was a relationship between NO2 and NO2/SO2 tolerance. Chronic NO2 fumigation of Lolium perenne L. was shown to have apparently beneficial effects such as increased growth, increased chlorophyll content and reduced rate of senescence. The Rainham population of this species appears to have a requirement for low concentrations of NO, in the atmosphere. There was an indication that plants which were most tolerant of acute doses of NO2 were those which most benefited from low concentrations of NO2L. perenne and D. glomerata were adversely affected by chronic exposure to a mixture of NO2 and SO2 The Rainham populations of both species were more tolerant of the mixture than bred cultivars. Chronic NO2/SO2 injury was found to be more severe when soil nitrogen was high.