Inhibition of Curvature Responses by Shunting the Inherent Electrical Field.

In studies of the bioelectric fields of the onion root, ROSENE (2) found that the magnitude of the longitudinal polarity was decreased or shunted when a jacket of tap water was placed around a segment of the root between the contacts. When the shunt was removed, the polarity quickly returned to practically its former level. Similar results were obtained by WnKs and LUND (7) from their experiments with the Avena coleoptile. They observed that filling isolated sheaths (taken from 34 to 36 millimeter seedlings) with Shive's solution caused the magnitude of the external longitudinal polarity to be decreased from 40 to 60 to less than 10 millivolts. As in the onion root, when the solution was removed from the inside of the sheath, the electrical polarity was promptly restored. These facts were presented as proof of internal shunting of some of the polar cells which contribute to the longitudinal electrical polarity of the sheath. WILKs and LUND (7) also reported preliminary experiments in which the central cavities of isolated coleoptiles were filled with various solutions and then exposed unilaterally to 400 meter candles of white light. Coleoptiles that were filled with Shive's solution did not show any bending response, and those filled with distilled water curved only slightly when compared to the curvature of the air-filled sheaths. Since it is known from previous data that electrolytic solutions, such as Shive's, short-circuit the electrical polarity, these experiments indicate that the inherent electrical field is a fundamental prerequisite for the growth curvature processes. The purpose of the present paper is to present supplementary data which show the quantitative effects of short-circuiting the inherent electrical field, using different concentrations of Shive's solution, on the various tropic responses of the Avena coleoptile.