Uptake and metabolism of sulphur dioxide by Arabidopsis thaliana

Arabidopsis thaliana (L.) Heynh. was exposed to various concentrations of SO₂ during almost the entire life cycle. No negative effects of SO₂ on shoot biomass production were observed. There was a linear relation between the deposition of SO₂ and the atmospheric SO₂ concentration. Sulphur accumulated substantially in the shoots upon SO₂ exposure. SO₂ was either oxidized to sulphate or converted into extra organic sulphur compounds in a sulphate to organic sulphur ratio of 3:1, independently of the atmospheric SO₂ concentration. Exposure to SO₂ resulted in an increase in water soluble non-protein sulphydryl content and a slight increase in the amount of glucosinolates, but both of these play a minor role as sinks for the excess sulphur. The ratio of total nitrogen to total sulphur decreased upon SO₂ , exposure as a result of the increased sulphate content. The organic nitrogen to organic sulphur ratio did not change upon SO₂ exposure, indicating no changes in the composition of sulphur-containing compounds.