Circadian rhythmicity in excised samanea pulvini: I. Sucrose-white light interactions.

The rhythmic movement of excised Samanea saman pulvini incubated in H(2)O or 50 mm sucrose was monitored during extended periods of white light (cool white fluorescent, 2,000 ft-c), darkness, or alternating white light (16 hr) and darkness (8 hr). In continuous white light, the rhythm damps at an intermediate angle after only one cycle, whether pulvini are incubated in sucrose or H(2)O. The rhythm also damps after the first cycle when darkened pulvini are incubated in H(2)O, but it persists for several cycles if sucrose is available. Sucrose depresses the mesor (average angle) during extended dark periods in Samanea, as in Albizzia julibrissin, but it increases the mesor if supplied during white light-dark cycles. With the latter irradiation schedule, oscillations persist for several cycles whether pulvini are supplied with H(2)O or sucrose, but closure is incomplete when pulvini are incubated in sucrose.