EFFECTS OF BISULFITE AND SULFATE UPON PHOTOSYNTHESIS IN SPHAGNUM

The effect of various concentrations of HSO3- and SO42- on photosynthetic O2 evolution in Sphagnum spp. was studied. Almost instantaneous reduction induced by HSO3-, the magnitude of which increased with concentration, were not reversed by additions of HCO3-. SO32- had no effect on O2 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 sulfite toxicity and to effects of sulfite on growth of Sphagnum spp.