The Effects of Bisulphite and Sulphate Upon Photosynthesis in Sphagnum

Summary The effect of various concentrations of HSO3‐ and SO42‐ on photosynthetic oxygen evolution in Sphagnum spp. was studied. Almost instantaneous reductions induced by HSO3‐, the magnitude of which increased with concentration, were not reversed by additions of HCO3‐. SO32‐ had no effect on oxygen evolution. The effect of HSO3‐ was markedly pH‐dependent, being much greater at lower pH. 14CO2 uptake was less sensitive to HSO3‐ than O2 evolution; low HSO3‐ concentrations enhanced 14CO2 fixation but never increased O2 evolution. 14CO2 fixation in the dark was also inhibited by 0·1 mM HSO3‐ but enhanced by lower concentrations. The results are discussed in relation to known mechanisms of sulphite toxicity and to effects of sulphite upon growth of Sphagnum spp.