Protoplasmic Potentials in Halicystis Iii. the Effects of Ammonia by L. R. Blinks

The large potential difference measurable across the protoplasm of impaled multinucleate cells of the alga ttalicystis has been described in preceding papers.t, ~ This is called "protoplasmic" since it is, to a large extent, independent of concentration gradients between sea water and the vacuolar sap. Thus a large P.D. persists when natural or artificial sap is applied externally, both in the species containing much KC1 and in that containing little. Dilution and concentration of the sea water, or of many of its constituents, provided a reasonable physiological balance of salts is maintained, also have little effect, after certain transient changes have occurred. However, such applications at the outer surface may not immediately affect potentials at the inner surface, or within the protoplasm itself. To study these, internal changes must be produced. The effect of naturally differing cell saps on the vacuolar surface has already been noted3 There remain as experimental changes: (1) direct alteration of the cell sap by injection or perfusion; (2) the penetration of substances into the cell from the sea water. Both of these methods have been employed, with marked effects upon the observed P.D. The results with ammonia, representing the penetration of a substance into the cell, are reported in the present paper. Being technically simpler to produce than the changes by sap perfusion, they were completed first. The results, however, are inherently more complex, since they involve not only the changes known to occur in the sap, but also unknown changes in the protoplasm across which the ammonia must pass to reach the vacuole. Some of the results of direct perfusion which bear upon the interpre-