Abstract
1. Growth of Chlorella sorokiniana in the presence of 7.5 mM sulfite, which halved the growth rate while doubling the superoxide dismutase (SOD; EC 1.15.1.1) content per cell, rendered the cells resistant to the toxic effects of 30 μM paraquat. 2. While increasing total SOD content, sulfite increased the relative amount of the H2O2-resistant manganese-containing SOD. 3. It appears that O2 may be involved in mediating the toxicity of SO2 in this green alga.