EARLY GRAVI-ELECTRICAL RESPONSES IN BEAN EPICOTYLS

The relationship between gravitropism and surface electrical potential s was studied using etiolated epicotyls of adzuki bean (Phaseolus angu laris). Early downward curvature (or transient positive gravitropic re sponse) was observed about 1 min after gravistimulation. The downward curvature was closely related to the speed of the subsequent upward cu rvature. Surface electrical potentials decreased cooperatively in a li mited region on the upper side within only 0.5 to 2 min. This is the e arliest event found so far to follow gravistimulation of intact epicot yls. The rapid change in the potential had a high correlation with the early downward curvature and also the subsequent negative gravitropis m. It is suggested that the rapid potential change plays an important role in gravity perception.