Abstract
Visible effects of the flow of direct current through the cells of Tradescantia and other plants bearing anthocyan indicators have been known since the studies of Kühne. 1 They are generally accepted 2 , 3 , 4 as evidence of a change of acidity at the opposite ends of each cell, in accordance with the well known behavior of these pigments as indicators. A repetition of such experiments, with a variety of plants (from about a dozen families), leads the writer to a different interpretation, namely, a migration of the pigment within the cell.
The typical results with one group of plants including Tradescantia (Zebrina), Commelina, Rhoeo (see also second group), Lippia, Plantago, Sonchus, beet and turnip, are as follows:
1. With uninjured cells, distant electrodes making contact to the tissue through agar, and low applied potential (1.5 to 6 volts in the epidermal strips as used) there is no apparent effect of current flow, the pigment remaining uniformly distributed throughout the cells and unchanged in hue.
2. With higher potentials (10 to 20 volts, probably causing some injury), or with low potentials in cells injured by chloroform or otherwise, there is a marked migration of pigment in most cells of the tissue toward the positive pole (anode). This results in concentrating it at the anodal end of each cell, the pink pigment there becoming deeper red in appearance, and depleting it at the cathodal end. The latter becomes almost clear, or more usually pale green, the general hue of the tissue when not pigmented with anthocyan. This green seems to have been taken to be due to increased alkalinity, but the expected intermediate hues, purple and blue, are not seen and the green is always pale.
3. Moreover the same (anodal) migration of pigment occurs in cells which have been immersed in ammonia, or other alkali.
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