Movements of K⁺ during shutting and opening of the trap-lobes in aldrovanda vesiculosa

K⁺ movements during the shutting and subsequent opening of trap-lobes in Aldrovanda vesiculosa were measured using ⁸⁶Rb as a tracer for K⁺. Immediately after the shutting, a large amount of ⁸⁶Rb pre-loaded in the trap-lobes was detected in the hollow space inside the shut trap. This may indicate that much of the K⁺ in the active motor cells leaks out during the shutting, resulting in turgor loss in the cells. ⁸⁶Rb(K⁺) uptake in the trap was active. During the opening process, enhanced ⁸⁶Rb uptake was observed. The time course of this uptake was similar to that of the opening of the trap-lobes, and both courses were accelerated by IAA. Enhanced K⁺ uptake may restore the turgor in active motor cells. The quantity of K⁺ that moved during the shutting or opening was estimated as 20% of that in the active motor cells in the open state of the trap-lobes. The K⁺ efflux across the membranes of the active motor cells may be caused by a large increase in bulk flow triggered by an action potential, and was estimated as 6,200 pmol.cm^-2.