Extreme pollution sensitivity of grasses when SO₂ and NO₂ are present in the atmosphere together

Abstract

PREDICTIONS of the possible effects of atmospheric pollution on vegetation have usually been based on the results of experiments in which plants were fumigated in the laboratory. For many years it was thought that exposures to SO₂ concentrations below 0.30 p.p.m. were not detrimental to higher plants^1,2, which led to the belief that this form of pollution is unlikely to cause any appreciable damage to crops in Britain where, even in heavily populated areas, monthly mean SO₂ concentrations are usually below 0.15 p.p.m., and daily means rarely exceed 0.30 p.p.m. (ref. 3). Recently, however, evidence has accumulated that concentrations of SO₂; below 0.15 p.p.m. can be damaging to plants^4–8, casting doubt on the comfortable conclusions drawn from earlier studies. We found that laboratory experiments can underestimate the amount of injury resulting in the field, and report here that combinations of SO₂ with NO₂ give more realistic effects.