Disappearance of Electric Spatial Pattern in a Bean Root under Circumstances in Nitrogen Gas

A spatial pattern of electric potential in the growing root was studied with a usual microelectrode and a multi-electrode measuring apparatus, which made possible a simultaneous measurement of electric potentials along the root. The pattern of surface electric potential disappeared along the entire root length when air surrounding the plant was replaced with nitrogen gas for about 2 h. Disappearance of a large peak of surface potential around 10 mm from the root tip preceded both the decrease in the growth speed and the change in pH of the aqueous medium to neutral in the elongation region, while this region showed a localized acidification in normal conditions. Supply of air recovered the spatial patterns of electric potential and pH. Proton accumulation within the cell wall following activation of H⁺ pumps was suggested to participate directly in the growth.