The Flower of Kalanchoe
The tiny red flowers of Kalanchoe blossfeldiana open and close at 23-hour intervals. They do this for a week even when plucked from the plant and placed in a vial of sugar water under constant green light, at a constant temperature. Though blind to green, the flower’s clock is sensitive to red light. By exposing the flower to red light of intensity several watts per square meter for minutes to hours, one disrupts the normal rhythmicity. In most cases, it recovers sufficiently within four days so that a phase shift can be measured.
KeywordsPhase Shift Light Pulse Circadian Clock Phase Singularity Stimulus Magnitude
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