Circadian clock in photoperiodic time measurement: a test of the Bünning hypothesis.
A technique has been developed for effectively separating the direct inductive effect of a light signal from its effect on the phase of the rhythm of sensitivity to photoperiodic induction. With this technique it has been shown that a 75-minute pulse of light per day, when appropriately positioned with respect to the circadian activity cycle of the sparrow Passer domesticus, is sufficient to produce a response normally produced only by long days. The results cannot be interpreted in terms of a requirement of an absolute amount of either darkness or light and offer strong confirmation of Bünning's hypothesis concerning the mechanism of photoperiodic time measurement.
D000818:Animals; D001522:Behavior, Animal; D001717:Birds / Q000502:physiology*; D002940:Circadian Rhythm; D003624:Darkness; D008027:Light; D008297:Male; D009929:Organ Size; D013737:Testis