The Experimental Production of Double Peaks in Chara Action Curves and Their Relation to the Movement of Potassium

The action curve in Chara seems to depend (as in Nitella) on the outward movement of K(+) from the sap. Presumably the increase in permeability in the inner protoplasmic surface and the outward movement of K(+) destroy the concentration gradient of K(+) across the inner protoplasmic surface. Hence the outwardly directed P.D. disappears, causing the rise (spike) of the action curve. The outer protoplasmic surface is normally insensitive to K(+). But when it is made sensitive to K(+) by treatment with guanidine the outwardly moving K(+) sets up a positive P.D. on reaching the outer surface and this causes the action curve to fall, producing a peak. Then the curve has 2 peaks, the second being due to the process of recovery. The action curve thus comes to resemble that of Nitella in which the outer protoplasmic surface is normally sensitive to K(+).