Kinetics of the light-induced georeactivity of maize roots.

Apical root segments of Zea mays L. cv. Orla 264 undergo some geotropic curvature in complete darkness but the curvature increases considerably if prior to geostimulation the segments are given a light pretreatment. If the light treatment is follwed by a dark treatment before the root is geostimulated the light-induced response is not changed by dark periods up to 2 h but declines with longer ones, and disappears completely after 5 h of darkness.