Shortening of the Period of the Circadian Rhythm by a K+ Channel Blocker, Tetraethylammonium, in the Duckweed Lemna gibba G3

The period of the circadian rhythm of uptake of K+ by Lemna gibba strain G3 (duckweed), cultured in a flow medium, was shortened by continuous application of 0.5 mM tetraethylammonium chloride (TEA), which functions as a K+ channel blocker in both animal and plant cells. Other quaternary ammonium ions shortened the period of the rhythm in direct proportion to their ability to block K+ channels in cells of the nervous system. Ca2+ appears to be specific in its ability to antagonize this action of TEA and of its analogues.