Localization of Hydrogen Ion and Chloride Ion Fluxes in Nitella

Alternating bands of acid and base formation have been detected along the length of the internodal cell of Nitella clavata when it is illuminated, while in the dark this phenomenon is minimal. Chloride influx occurs only or largely in the acid-extruding regions, and this is also a light-dependent ion movement. Chloride efflux is slightly dependent on illumination and is not localized as are H⁺ efflux and Cl^- influx. The results obtained support Kitasato's (1968) proposal that a large passive H⁺ influx is balanced by an active efflux of this ion. Transport mechanisms suggested by the correlations of Cl^- and HCO₃^- influxes with H⁺ extrusion are discussed.