Abstract
In a previous paper 1 it was shown that there was a definite relation between the penetration of oxidation-reduction indicators into cells of Valonia macrophysa and their position in the oxidation-reduction scale. Those dyes which were at the electro-positive end of the scale penetrated very readily, while those which were farther down towards the electro-negative end did not penetrate. The former were represented by the indophenols, which were reduced in the sap; and the thiazines, which were not reduced. The latter included the indigo-sulphonates, which did not penetrate.
The question was then raised whether the position of the dye on the oxidation-reduction scale was the determining factor in its penetration. Fortunately Rapkine, Struyk and Wurmser 3 have determined the potentials of some vital dyes on the Eh scale, and found that Janus green and neutral red are more electro-negative than any of Clark's dyes; in fact the neutral red system lies very near to the H electrode. These 2 dyes were, therefore, used in further penetration studies.
About one dozen small plants of Valonia ventricosa which had been kept in the laboratory for some months and seemed to all outward appearances to be normal living cells, were placed in solutions of sea water containing 0.001% Janus green and buffered with Clark's buffers at various pH values from 5.8 to 9.0. The total M concentration of buffer was 0.009. The temperature was 25° C. The sap was examined at various intervals up to 12 hours and in no case was the dye found in the sap in detectable amounts either in the oxidized or the reduced state.
Other plants were placed for one hour in a solution of 0.001% Grübler's neutral red dissolved in sea water containing buffers as previously described at pH 5.8.
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