On the mechanism of 60-Hz electric field induced effects in Pisum sativum L. roots: vertical field exposures.

Roots of Pisum sativum L. were chronically exposed to 60-Hz vertical electric fields ranging from 150 to 450V/m in an aqueous medium whose conductivity was approximately 0.07 S/m. Control and exposed roots were grown concomitantly in the same tank whose medium was continuously circulated and maintained at 19 degrees C. The experiments were conducted blind. Root growth rates were determined daily and the mitotic index was determined for various intervals over a 24-h period, ranging from 12 h before to 12 h after electrode energization. Root growth rates were affected in a dose dependent relationship by exposures greater than 250 V/m. Mitotic indices were not affected by 150 V/m but were affected at 350 V/m; the former exposure did not alter root growth rates, the latter did. The growth rates of vertically exposed roots were compared to those of horizontally exposed roots; the former are more sensitive at a given field strength. The observations are consistent with the postulate that the electric field acts upon the cell through a perturbation of the transmembrane potential.