Electrical Correlates of Growth in Corn Roots *

All mature living organisms possess relatively constant potential differences ibetween any two points. To some extent, at least, these standing potential differences are a measure of an electrical reservoir, which may be called upon by the various organ systems during activity. They can be measured at all times during life and disappear upon death. They are arranged in characteristic patterns and define in a rigorous sense an electrodynamic field within the organism. Field changes have been shown to occur as correlations of fundamental biological activity. This is particularly true of the phenomenon of growth. The relationship has been pointed out by Mathews,8 by Child,6 and by Lund.7 Burr and Hovland3 ' extended these studies to the developing embryos of salamander and chick, and Burr and Hammett to the development of Obelia.2 More recently, Burr and Bullock' have reported continuous records of e.m.f. in developing salamander eggs. In the original study on Obelia, it was noted that the potential difference between the base of a single individual and the apex of the embryo steadily increased in magnitude during development with the base positive and the growing point negative. By the time the cup of the hydranth was formed, this potential tended to reach a maximum. However, with the advent of differentiation within the hydranth, a characteristic change in the potential difference was observed. At this time, protoplasm can frequently be observed to ebb and flow within the hydranth in continuous pulsations. Correlated with these pulsations were definable rises and falls in the potential difference which, so far as the eye could see, seemed to be simultaneous with the protoplasmic movement. In the salamander (Burr and Bullock') it was shown that during the early stages of development the potential differences were remarkably constant, showing no significant changes with cell division. Presumably this was due to the over-all character of the measurements. However,