Potassium Channels in Samanea saman Protoplasts Controlled by Phytochrome and the Biological Clock

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Science  14 May 1993:
Vol. 260, Issue 5110, pp. 960-962
DOI: 10.1126/science.260.5110.960


Leaflet movement in legumes depends on rhythmic, light-regulated ion fluxes in opposing regions of the leaf-moving organ. In flexor and extensor protoplasts from Samanea saman Merrill, opening and closing of K+ channels were rhythmic in constant darkness. When channels were open in flexor protoplasts they were closed in extensor protoplasts, and vice versa. The rhythms were shifted by a delay in the onset of constant darkness, a response typical of endogenous circadian rhythms. During the light period, the channels in flexor protoplasts were sensitive to red light that was followed by premature darkness; phytochrome was implicated as the photoreceptor.

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