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Science 10 November 1967:
Vol. 158. no. 3802, pp. 787 - 788
DOI: 10.1126/science.158.3802.787
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Articles

Membranes of Valonia ventricosa: Apparent Absence of Water-Filled Pores

John Gutknecht 1

1 School of Biological Sciences, University of East Anglia, Norwich, England

Osmotic and diffusional permeabilities to water have been measured in internally perfused cells of Valonia ventricosa. The osmotic and diffusional permeability coefficients for the protoplast are identical, 2.4 x 10-4 centimeter per second. Thus, both osmotic and diffusional flows can occur by the same mechanism, that is, by diffusion; and there is no need to postulate the existence of water-filled pores in the membranes of this cell. Supporting evidence for this conclusion is the absence of solvent-solute interactions, that is, "solvent drag," for water, urea, and methanol crossing the protoplast of Valonia.


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Science. ISSN 0036-8075 (print), 1095-9203 (online)