Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954 electrolytesinbi00shan Year: 1955 GEORGE T. SCOTT AND HUGH R. HAYWOOD 59 Efifect of External Sodium on Potassium Accumulation in Ulva. IL is of con- siderable importance to determine whether or not the potassium-accumulating mechanism is passive, dependent upon and secondary to the sodium-secreting mechanism, or whether it is active and independent of sodium secretion. To this end the following type of experiment was carried
Electrolytes in biological systems, incorporating papers presented at a symposium at the Marine Biological Laboratory in Woods Hole, Massachusetts, on September 8, 1954 electrolytesinbi00shan Year: 1955 GEORGE T. SCOTT AND HUGH R. HAYWOOD 59 Efifect of External Sodium on Potassium Accumulation in Ulva. IL is of con- siderable importance to determine whether or not the potassium-accumulating mechanism is passive, dependent upon and secondary to the sodium-secreting mechanism, or whether it is active and independent of sodium secretion. To this end the following type of experiment was carried out. Samples of Ulva fronds were repeatedly suspended in isotonic sucrose for 2 to 3 hours, at which time the cells had lost about 85 of their sodium and potassium (figs. 19 and 20). At this time half the samples were transferred to complete natural sea water, while the others were placed in sodium-free Allen's artificial sea water, isotonicity maintained by the addition of sucrose. Potassium reaccumulation was followed in the two groups by removing samples at various times over a 6 Of 1 1 1 1 1 1 1 TRANSFERRED TO SEA WATER AT I8°C 200 HOURS 250 300 350 Fig. 18. Influence of cold (2-5°C) on the potassium and sodium content of Valonia macro- physa. At the time indicated by the arrow the cells were transferred to running sea water at i8°C in the light. 24-hour period. Two features of the data are outstanding: i) the potassium reaccumulation is, within experimental error, linear; and 2) the presence of sodium in the external fluid made no measurable difference in the rate of potas- sium reaccumulation. It is noteworthy that in other experiments the potassium reaccumulation was complete to the control level. The sodium concentration in those samples returned to complete sea water is seen to have reached the control level within the time at which the first samples of this series were re- moved; the curve for re-entry of sodium, then, is probably steeper than the one shown here
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