Summary
In C. rubrum, the amount of flowering that is induced by a single dark period interrupting continuous light depends upon the duration of darkness. A rhythmic oscillation in sensitivity to the time that light terminates darkness regulates the level of flowering. The period length of this oscillation is close to 30 hours, peaks of the rhythm occurring at about 13, 43 and 73 h of darkness.
Phasing of the rhythm by 6-, 12- and 18-h photoperiods was studied by exposing plants to a given photoperiod at different phases of the free-running oscillation in darkness. The shift in phase of the rhythm was then determined by varying the length of the dark period following the photoperiod; this dark period was terminated by continuous light.
With a 6-h photoperiod the timing of both the light-on and light-off signals is shown to control rhythm phasing. However, when the photoperiod is increased to 12 or 18 h, only the light-off signal determines phasing of the rhythm. In prolonged periods of irradiation-12 to 62 h light—a “durational” response to light overrides any interaction between the timing of the light period and the position of the oscillation at which light is administered. Such prolonged periods of irradiation apparently suspend or otherwise interact with the rhythm so that, in a following dark period, it is reinitiated at a fixed phase relative to the time of the light-off signal to give a peak of the rhythm 13 h after the dusk signal.
In daily photoperiodic cycles rhythm phasing by a 6-h photocycle was also estimated by progressively increasing the number of cycles given prior to a single dark period of varied duration.
In confirmation of Bünning's (1936) hypothesis, calculated and observed phasing of the rhythm controlling flowering in c. rubrum accounts for the photoperiodic response of this species. Evidence is also discussed which indicates that the timing of disappearance of phytochrome Pfr may limit flowering over the early hours of darkness.
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References
Brest, D. E., Hoshizaki, T., Hamner, K. C.: Rhythmic leaf movements in Biloxi soybean and their relation to flowering. Plant Physiol. 47, 676–681 (1971).
Brown, F. A.: A unified theory for biological rhythms: rhythmic duplicity and the genesis of “circa” periodisms. In: Circadian clocks, p. 231–261 (J. Aschoff, ed.). Amsterdam: North-Holland 1965.
Bünning, E.: Die endonome Tagesrhythmik als Grundlage der photoperiodischen Reaktion. Ber. dtsch. bot. Ges. 54, 590–607 (1936).
Bünning, E.: Biological clocks. Cold Spr. Harb. Symp. quant. Biol. 25, 1–9 (1960).
Bünning, E.: Circadian rhythms and the time measurement in photoperiodism. Cold Spr. Harb. Symp. quant. Biol. 25, 249–256 (1960).
Bünning, E.: Common features of photoperiodism in plants and animals. Photochem. and Photobiol. 9, 219–228 (1969).
Bünsow, R. C.: The circadian rhythm of photoperiodic responsiveness in Kalanchöe. Cold Spr. Harb. Symp. quant. Biol. 25, 257–260 (1960).
Cumming, B. G.: Evidence of a requirement for phytochrome-Pfr in the floral initiation of Chenopodium rubrum. Canad. J. Bot. 41, 901–926 (1963).
Cumming, B. G.: Circadian rhythmic flowering responses in Chenopodium rubrum: effects of glucose and sucrose. Canad. J. Bot. 45, 2173–2193 (1967).
Cumming, B. G.: Chenopodium rubrum L. and related species. In: The induction of flowering (L. T. Evans, ed.), p. 156–189. Melbourne: Macmillan 1969a.
Cumming, B. G.: Photoperiodism and rhythmic flower induction: complete substitution of inductive darkness by light. Canad. J. Bot. 47, 1241–1250 (1969b).
Cumming, B. G., Hendricks, S. B., Borthwick, H. A.: Rhythmic flowering responses and phytochrome changes in a selection of Chenopodium rubrum. Canad. J. Bot. 43, 825–853 (1965).
Cumming, B. G., Wagner, E.: Rhythmic processes in plants. Ann. Rev. Plant Physiol. 19, 381–415 (1968).
Denney, A., Salisbury, F. B.: Separate clocks for leaf movements and photoperiodic flowering in Xanthium strumarium L. (Cocklebur). Plant Physiol. 46 Suppl., 26 (1970).
Evans, L. T., King, R. W.: Role of phytochrome in photoperiodic induction of Pharbitis nil. Z. Pflanzenphysiol. 60, 277–288 (1969).
Halaban, R.: The circadian rhythm of leaf movement of Coleus blumei x C. frederici, a short-day plant. II. The effects of light and temperature signals. Plant Physiol. 43, 1887–1893 (1968a).
Halaban, R.: The flowering response of Coleus in relation to photoperiod and the circadian rhythm of leaf movements. Plant Physiol. 43, 1894–1898 (1968b).
Hamner, K. C.: Photoperiodism and circadian rhythms. Cold Spr. Harb. Symp. quant. Biol. 25, 269–277 (1960).
Hillman, W. S.: Carbon dioxide output as an index of circadian timing in Lemna photoperiodism. Plant Physiol. 45, 273–279 (1970).
Ioffe, A. A.: Correlation of leaf movement and flowering in Perilla oleifera. Dokl. Akad. Nauk. SSSR, Bot. Sci. 180, 92–94 (1968).
King, R. W.: Time measurement in the photoperiodic control of flowering. Ph.D. Thesis. Univ. Western Ontario, Canada (1971).
Papenfuss, H. D., Salisbury, F. B.: Aspects of clock resetting in flowering of Xanthium. Plant Physiol. 42, 1562–1568 (1967).
Pittendrigh, C. S.: Circadian rhythms and the circadian organization of living systems. Cold Spr. Harb. Symp. quant. Biol. 25, 159–184 (1960).
Pittendrigh, C. S.: The circadian oscillation in Drosophila pseudoobscura pupae: a model for the photoperiodic clock. Z. Pflanzenphysiol. 54, 275–307 (1966).
Pittendrigh, C. S., Minis, D. H.: The entrainment of circadian oscillations by light and their role as photoperiodic clocks. Amer. Naturalist 97, 261–294 (1964).
Takimoto, A., Hamner, K. C.: Effect of temperature and preconditioning on photoperiodic responses of Pharbitis nil. Plant Physiol. 39, 1024–1030 (1964).
Takimoto, A., Hamner, K. C.: Effect of double red light interruptions on the photoperiodic response of Pharbitis nil. Plant Physiol. 40, 855–858 (1965).
Wagner, E., Cumming, B. G.: Betacyanin accumulation, chlorophyll content, and flower initiation in Chenopodium rubrum as related to endogenous rhythmicity and phytochrome action. Canad. J. Bot. 48, 1–18 (1970).
Wilkins, M. B.: The effect of light upon plant rhythms. Cold Spr. Harb. Symp. quant. Biol. 25, 115–129 (1960).
Winfree, A. T.: Integrated view of resetting a circadian clock. J. theor. Biol. 28, 327–374 (1970).
Zimmer, R.: Phasenverschiebung und andere Störlichtwirkungen auf die endogen tagesperiodischen Blütenblattbewegungen von Kalanchöe blossfeldiana. Planta (Berl.) 58, 283–300 (1962).
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King, R.W., Cumming, B.G. Rhythms as photoperiodic timers in the control of flowring in Chenopodium rubrum L.. Planta 103, 281–301 (1972). https://doi.org/10.1007/BF00386700
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DOI: https://doi.org/10.1007/BF00386700