Protoplasmic Potentials in Halicystis. VI. Role of Ammonia in Potential Reversal by Perfusion.

Abstract

Earlier papers1 have described the reversal of the normally positive potential difference across the protoplasm of impaled cells of Halicystis osterhoutii (Bermuda) both by exposure to ammonia (or other weak bases) and by perfusion of the vacuole with more alkaline sap or sea water. The author was then inclined to explain the former effect by the latter, since penetration of ammonia raised the vacuolar pH. One difficulty of this interpretation was that the Californian species, H. ovalis, did not show such reversal on perfusion with sea water at pH 8.0 or higher, although reversing well on exposure to ammonia. This difference between the species now seems reconciled by referring the effects in both cases to the penetration of ammonia into the protoplasm. This is shown in H. ovalis by introducing into the perfusing fluid a trace of NH4Cl; at pH 5.0, the normal acidity of the sap, no effect is observed, but if sea water now is perfused at pH 8.0, reversal of potential often results. Then as perfusion is cont...