Ionic Currents During Regeneration of Thallus and Rhizoid From Cell Segments Isolated From the Marine Alga Bryopsis

Cell segments isolated from the unicellular marine alga, Bryopsis plumosa, regenerated or protruded thallus (T) at one cut end and rhizoid (R) at the other cut end. Using a vibrating probe, we measured endogenous ionic currents associated with these events. Prior to the protrusion of T and R, the currents changed in various ways. When the T and R protruded at the cut ends of the segments, we detected an inwardly directed current at the regions of T and R, and an outwardly directed current in other parts of the cell segment. Both currents were strongly affected by decreases in external concentrations of Cl^-, suggesting that a large part of the currents was carried by C1^-. In addition, these currents decreased with a decrease in external concentrations of Mg²⁺, and were also reversibly eliminated by two metabolic inhibitors. This evidence suggests that the C1^- -migration system involves an energy-dependent and Mg²⁺ -dependent process. In parallel with the generation of these currents, turgor pressure reached a maximum prior to the protrusion of T and R. The relationship between the generation of the currents, the generation of the maximum turgor pressure, and the protrusion of T and R is discussed.