Bisulfite compounds are shown to be nonspecific inhibitors of photosynthetic processes and of ion transport in green tissues. CO/sub 2/ fixation and light-dependent transient changes in external pH are inhibited about 50% by 5 x 10/sup -4/M glyoxal-Na-bisulfite. Chloride uptake in the light and in the dark is inhibited to the same extent at this concentration. At 5 x 10/sup -3/M the inhibitor reduces ATP levels in the light and in the dark, and the effects on glycolate oxidase and PEP carboxylase are observed. The extent of inhibition is dependent on time of treatment with glyoxal-Na-bisulfite and freshly prepared NaHSO/sub 3/ is equally as effective as the addition compound. Possible explanations of the bisulfite effects and the relationships to SO/sub 2/ effects on photosynthesis are discussed.