Koziol, M. J., Shelvey, J. D. and Beedham, B. 1986 Uptake of S'v anions and the induction of gaseous emissions in leaf segments of SO2-sensitiveand resistant genotypes of Lolium perenne L.—J.exp. Bot. 37: 556–571. At pH 3·0 and over a range of concentrations from 5 to 100 mol m−3 NaHSO2 the SO2 genotype (S23) took up less HSO3- and showed a lower metabolic threshold for the induction of gaseous emissions than the SO2 genotype (BR). Emission of H2S from leaf segments of S23 was induced at an estimated sulphite concentration of 605 ng g−1 fr. wt. compared with 932 ng g−1 fr. wt. in BR. Although the uptake of sulphite by leaf segments incubated on NaHSO3 solutions at pH 7·0 was similar to that of leaf segments incubated at pH 3·0, very little ethane, ethylene or H2S were emitted. A free radical scavenging mechanism is proposed to explain these observations. At pH 6·0 and concentrations of NaHSO3 equivalent to low to moderate exposure concentrations of gaseous SO2 BR took up more sulphite than S23. Uptake in both genotypes was partially inhibited by CCCP and by pre-loading the leaf segments with sulphate, indicating an active uptake mechanism transporting both sulphate and sulphite.