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Journal of Experimental Biology 8,124-132 (1931)
Published by Company of Biologists 1931

Potential Differences Across Natural Membranes Separating Unlike Salt Solutions

S. C. BROOKS ¹, A. C. GIESE ¹, and R. I. GIESE ¹

¹ Dept. of Zoology, Univ. of California, and Hopkins Marine Station, Stanford University

1. When the lower epidermis of the bulb scale of the onion separates 0.1M and 0.01M solutions of KCl, NaCl, or LiCl a transient "concentration" potential difference was observed, whose magnitude decreased in the order: K > Na > Li.

2. The potential difference of 0.1M: 0.01M CaCl₂ is small and opposite in sign to that of the above chains.

3. When the epidermis separates like concentrations of chlorides of K, Na, and Li a cation "chemical" potential difference arises which is low but steady.

4. When K-salts with different anions are present on the opposite sides of the membrane, the anion "chemical" potential difference is small or lacking.

5. These facts are most simply accounted for by assuming that the epidermis is a mosaic of cation and anion permeable areas, the permeability to alkali metal cations much exceeding that for calcium ion or the anions tried.

6. It is pointed out that the cell walls may perhaps participate in the production of the bioelectric potentials observed in other plants.