Abstract
Electric currents have been shown to be capable of directing or determining the growth of certain organisms of simple symmetry. 1 , 2 , 3 The present is a report of experiments in which the application of direct electric current resulted in partial death of the organism; the effect being localized in a polar fashion. The results given below were obtained with the Bryophyte Conocephalus. Lunularia and Marchantia reacted similarly but not as definitely.
The plants were cleaned. Most of the rhizoids and the apex and base were clipped off. Current was applied through an agar bed (usually containing nutrients) upon which the plants were placed in intimate contact. It was found that death occurred in that part of the plant which lay toward the anode. This effect was not due to the creeping of toxic materials from the electrodes as suitable precautions were taken. Also, successive rows throughout the experimental dish were similarly affected while the region toward the cathode remained alive in all plants.
The extent of the dead region increased with greater current density; also with greater duration of exposure. Larger pieces were more susceptible than small, i. e., the percentage dead region/plant size was greater. No difference was detected in quantity of effect between plants oriented in opposite directions; that is, apex and base were equally susceptible when turned toward the anode. Regeneration did not, of course, occur toward the anode, but was not absent elsewhere. As a result new growths were more frequently seen on plants turned with apex toward the cathode.
This report is based on 116 plants which were subjected to direct currents of approximately ½ to 6δ for a period of time up to 350 hours. The dead region comprised 5 to 63% of the length of the thallus. Large plants (about 6 cm. long) showed about 20% more injury than small ones (1 cm. or less) for the same duration and density of current.
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