Removal by a Trace of Sodium of the Period Lengthening of the Potassium Uptake Rhythm Due to Lithium in <em>Lemna gibba</em> G3 <sup><a href="#fn1" rid="fn1" class=" fn">1</a></sup>
Abstract
The effect of Li on the period of the K uptake rhythm in the flow medium culture of the duckweed (Lemna gibba G3) was investigated under various ionic conditions. In the presence of Li at 0.2 millimolar or higher concentrations, the period was longer than the normal level of 25.4 hours by 2 hours. Li also lowered the amplitude of the rhythm. Although Na itself did not change any parameter of the rhythm, simultaneous application of Na at a very low concentration (20 micromolar) almost completely removed the effects of 0.5 millimolar Li on both the period and the amplitude. However, divalent cations (Ca and Mg) or Rb did not remove the Li action on the period. The effect of Li and its removal by Na corresponded to intracellular Li and Na levels. The period was prolonged when the duckweed contained more Li than 5 micromoles/gram fresh weight. But the Li effect was cancelled when the in vivo Na level was greater than one-fifth that of Li, even if the Li level exceeded over 5 micromoles/gram fresh weight.
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