Accumulation of Ions. Further Proof of Non-Equilibrium Condition in Valonia. ∗

Abstract

In a previous paper 1 I reported that when living cells of Valonia macrophysa were immersed for periods of 2-3 days in sea water to which had been added isotonic NaCl solution (10-50% by volume) there occurred an increase in the concentration of potassium and a decrease in that of sodium relative to that of chloride. Since these changes were in the direction opposite to those made in the composition of the external medium, it was concluded that this experiment furnished crucial proof that the normal condition in Valonia was not an equilibrium state. The validity of the data has been doubted by Cole on statistical grounds, 2 and by Jacques and Osterhout on experimental grounds. 3 I have therefore repeated my experiments in the endeavor to meet these criticisms.

Experiments were done on Valonia macrophysa at Naples, which tended to confirm my earlier results, but they were unsatisfactory statistically. Recently similar experiments were done on specimens of Valonia ventricosa at Tahiti. These specimens were extraordinary in the perfection of their selective permeability to ions: normal sap was found to consist of a KCl solution about 0.61 M and over 99% pure; Ca, Mg, and Na were present in concentrations of about 2, 1, and 1 mM/1, respectively.

Analyses were made by the methods previously described 4 except that K was determined by the cobaltinitrite method of Hibbard and Stout, 5 which was found by appropriate tests to be as accurate as the chloroplatinate method and much quicker. Na, being determined as the difference between total K + Na sulfates and K, is so small as to lie almost within experimental error. The negative values for Na might be due to this alone, or they might be due to a systematic error of less than 1% in one of the 2 directly determined values. The samples are not adequate for direct Na deter-mination.†

Table I shows that when a relatively slight change was made in the sea water, as in the 9:1 mixture whose K concentration was 0.010 M, and cells were exposed to this solution for only 3 days, the expected increase in the ratio of K/Cl occurred. The decrease in Na/Cl is worth noting, even though the uncertainty as to the figures for Na would make it, if taken alone, unreliable. In experiments lasting 3 days where a greater change was made in the sea water (K < 0.010 M), which thus correspond to the shortest experiment of Jacques and Osterhout, the result is like theirs in showing decrease in K/Cl. Experiments of duration shorter than 3 days had to be omitted because of lack of material, while those of longer duration again show a decrease in K/Cl. Since Jacques and Osterhout made all their determinations on cells exposed for 3 or more days to a solution containing 0.006 GM/1 of K it will be seen that in those of our experiments which were substantially similar we both find a decrease in K/Cl.