Abstract
The period (∼3-5 min) of the ultradian rhythm of the lateral leaflet movement of Desmodium motorium is strongly lengthened (≤30-40%) by the K+ channel blocker tetraethylammoniumchloride (20, 30, and 40 mM) and vanadate (0.5 and 1 mM), which is an effective inhibitor of the plasma membrane-bound H+ pump. The alkali ions K+, Na+, Rb+, and Cs+ (10-40 mM) shorten the period only slightly (≤ 10–15%). Li+ (5-30 mM), however, increases the period of the leaflet rhythm drastically (≤80%). We concluded that the plasmalemma-H+-ATP-ase-driven K+ transport through K+ channels is an essential component of the ultradian oscillator of Desmodium, as has been proposed for the circadian oscillator.