THE CONCENTRATION EFFECT WITH VALONIA: POTENTIAL DIFFERENCES WITH CONCENTRATED AND DILUTED SEA WATER

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Abstract
Electrical connection with the vacuole of a cell of Valonia macrophysa is established by impaling the cell on a fine glass capl.llary filled with artificial sap; on standing, the protoplasm becomes sealed to the glass. The P. D. between the interior of the cell and concentrated sea water (up to 1.5 times the strength of sea water) or diluted sea water (down to 0.2 times the strength of sea water) made isotonic with glycerol, is given by the equation: P.D. = P.D.s.w. + 2/3 RT/F In 1/concn. relative to that of s.w., where P.D.s.w. is the value (5.-8.5 mv.) observed with natural sea water. The sign is that of the interior of the cell. While these P.D.''s may be stable for some hrs., brief exposure to very concentrated or very dilute sea water, or to hypotonic solutions, leads to reversal of the sign of the P.D. The concentration effect is due mainly to the NaCl in the sea water. It is suggested that the factor of 2/3 in the formula represents the difference betwen the transfer numbers of Cl- and Na+ in the protoplasm; in this case, it is necessary to assume for Cl- a mobility 5 times as great as that of Na+.

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