Uptake and metabolism of sulphur dioxide by Arabidopsis thaliana.

Arabidopsis thaliana (L.) Heynh. was exposed to various concentrations of SO during almost the entire life cycle. No negative effects of SO on shoot biomass production were observed. There was a linear relation between the deposition of SO and the atmospheric SO concentration. Sulphur accumulated substantially in the shoots upon SO exposure. SO 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 SO concentration. Exposure to SO 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 SO , exposure as a result of the increased sulphate content. The organic nitrogen to organic sulphur ratio did not change upon SO exposure, indicating no changes in the composition of sulphur-containing compounds.