Movements of K+ during Shutting and Opening of the Trap-Lobes in Aldrovanda vesiculosa

K⁺ movements during the shutting and subsequent opening of trap-lobesin Aldrovanda vesiculosa were measured using ⁸⁶Rb as a tracerfor K⁺. Immediately after the shutting, a large amount of ⁸⁶Rbpre-loaded in the trap-lobes was detected in the hollow spaceinside the shut trap. This may indicate that much of the K⁺in the active motor cells leaks out during the shutting, resultingin turgor loss in the cells. ⁸⁶Rb(K⁺) uptake in the trap wasactive. During the opening process, enhanced ⁸⁶Rb uptake wasobserved. The time course of this uptake was similar to thatof the opening of the trap-lobes, and both courses were acceleratedby IAA. Enhanced K⁺ uptake may restore the turgor in activemotor cells. The quantity of K⁺ that moved during the shuttingor opening was estimated as 20% of that in the active motorcells in the open state of the trap-lobes. The K⁺ efflux acrossthe membranes of the active motor cells may be caused by a largeincrease in bulk flow triggered by an action potential, andwas estimated as 6,200 pmol.cm^–2. ¹ This paper is dedicated to the memory of Professor Joji Ashidawho established the physiology of rapid movement in Aldrovandavesiculosa. (Received July 22, 1982; Accepted November 11, 1982)