#temporal isolation

[temporalisolation]

Temporal Isolation

Temporal Isolation

[chronoclippings]

As a test of the hypothesis that leaf rhythms were driven by a rhythmic environment rather than the product of an endogenous time-sense, R. Semon reared Acacia lophantha under a 12-hour day, consisting of 6 hours of light and 6 hours of darkness.  After several such cycles, he released the plants into constant light of an intensity dim enough to support prolonged free-running rhythms.  The plant clearly failed to entrain to the 12-hour day and free-ran with period that was about twice as long as the previous 12-hour light dark cycle. The results supported the notion that the plant had an inherited endogenous rhythm. The figure is taken from R. Semon (1905) Über die Erblichkeit der Tagesperiod. Biol. Zentralbl. Vol. 25, pp. 241-252.

[chronoclippings]

The leaf movements of Acacia lophantha (a.k.a. Paraserianthes lophantha), recorded under constant darkness by W. Pfeffer and first reported in his book “Die periodischen Bewegungen Der Blattorgane,” published in 1875.  The rhythm appears to decrease rapidly in amplitude as time passes.  This led Pfeffer to suggest that the rhythms were produced by external rhythmic cues that had after-effects on the leaves for a only few cycles.   The results were consistent with plant rhythms being a passive response to light/dark cycles.  But the complete absence of light leads to an alternative explanation, particularly for a plant.  The figure is taken from the second edition of B. M. Sweeney’s “Rhythmic Phenomena in Plants,” published by Academic Press in 1987.

[chronoclippings]

Human physiological and behavioral rhythms under temporal isolation recorded in an underground bunker consisting of a “comfortable bed-sitting room” attached to a shower and small kitchen. Circadian changes in urination, core body temperature, and sleep and wakefulness are apparent. The subject in this case was the author J. Aschoff.  From  J. Aschoff (1965) Circadian Rhythms in Man. Science. Vol. 148, pp. 1427-1432

[chronoclippings]

The effects of 10-min light pulses on the timing of wheel-running activity in the nocturnal flying squirrel Glaucomys volans kept under constant darkness. The pulse delivered at the time of activity onset on day five caused an obvious delay in the subsequent phase of wheel-running.  The pulse delivered just after the daily bout of activity on day 15 resulted in no obvious change in phase.  From P.J. De Coursey (1960) Daily Light Sensitivity Rhythm in a Rodent.  Science. Vol. 131, pp. 33-35

[chronoclippings]

The effect of light intensity on the free running rhythm of luminescence in Gonyaulax plyedra, a photosynthetic marine dinoflagellate.  From top to bottom, the intensity of continuous light was 120, 380, and 680 foot-candles.  There were two major effects of increased light intensity, a shortening of the period, from 24.5, to 22.8, to 22.0 hours, and a reduction in the amplitude of the oscillation.  For this reason, Sweeney and Hastings had to identify light intensities that would allow Gonyaulax to produce sustained high amplitude glowing rhythms under constant conditions.  The rhythms above, were measured after entrainment to a light/dark cycle (800 foot-candle days). From J.W. Hastings and B.M. Sweeney (1958) A Persistent Diurnal Rhythm of Luminescence in Gonyaulax Polyedra. Biol. Bull. Vol. 115, pp. 440-458.

[chronoclippings]

Jean Jacques d’Ortous de Mairan’s description of persistent daily leaf movements in Mimosa shielded from the environmental light/dark cycle, presented to the Royal Academy of Sciences in Paris, 1729.  

[magic-the-beefening]

Good behavior will get you your time privileges back.