Electrical polarity in embryos of wild carrot precedes cotyledon differentiation

Endogenous electrical currents traverse embryos of a higher plant, the wild carrot Daucus carota L. Current enters the apical pole and leaves the region near the presumptive radicle in the radially symmetric globular embryo. Current also enters the exposed surfaces of incipient globular embryos. This electrical polarity precedes differentiation of vascular tissue and cotyledon development. Localized current is observed at both growing ends of the embryos in subsequent stages of embryogenesis. Inward current is found at the cotyledons; outward current is found at the radicle/root. Exogenous indole-3-acetic acid (3 muM) reversibly inhibits these currents. Little current traverses the surface of intermediate regions of the embryo. The ionic gradients generated by these currents may be important in accumulation of metabolites and in other developmental processes within the embryo.