The Physiological Clock

Bünning, Erwin

doi:10.1007/978-3-662-22511-0

Cited by 202 publications

(132 citation statements)

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“…The results from these experiments agree with the classical Bunning hypothesis which mentions an endogenous circadian rhythm of sensitivity to light as the physiological basis for photoperiodism (Bunning 1973). The validity of a circadian basis for photoperiodic time measurement in birds is generally tested by resonance and nightinterruption experiments (see reviews , Follett 1973 ;Farner 1975 ;Turek 1978).…”

Section: Introductionsupporting

confidence: 77%

“…Such results may best be interpreted on the basis of an endogenous circadian rhythm involvement in the 'photosensitivity' of the hypothalamo/hypophyseal/ gonadal system (Follett 1973 ;Farner 1975 ;Turek 1978). According to the external coincidence model, first developed by Bunning (1973), a photoperiodic induction occurs if and only if photophase coincides (repeatedly, daily or otherwise) with the photosensitive phase (= photoinducible phase, subjective night) of the circadian rhythm. In the present experiments presumably the birds of group II received 6 hr light at alternate cycles, and of group III were receiving 1 hr light period daily in the photosensitive phase and a response was obtained in both the groups.…”

Section: Resultsmentioning

confidence: 99%

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Circadian basis for the photoperiodic response in the male blackheaded bunting (Emberiza melanocephala)

Kumar

Tewary

1982

Proc Ani Sci

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Short day (6 hr light in a 24 hr cycle (LO 6 : 18» inhibits growth and development of the testes in male blackheaded buntings, whereas the same (6 hr) nonstimulatory photoperiods in a 36 hr cycle (LO 6 : 30) induce complete testicular recrudescence and development. In another experiment of 24 hr cycles, using the same (6 hr) main photoperiod, testes were stimulated when the dark period was interrupted by light at 12 to 13 hr after the onset of basic photoperiod (WLD 6 : 6 : 1 : 11). The results appear to conform to the tenets of the external coincidence model.

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Section: Introductionsupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Circadian basis for the photoperiodic response in the male blackheaded bunting (Emberiza melanocephala)

Kumar

Tewary

1982

Proc Ani Sci

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“…Many eukaryotes [3] and some prokaryotes [15,32] are capable of measuring time endogenously by what is generally referred to as the circadian biological clock. Although the molecular mechanism of this clock is not well understood, its importance becomes readily evident in the many examples of circadian rhythms [45,9,8,1 ].…”

Section: Introductionmentioning

confidence: 99%

Transcription ofCABII is regulated by the biological clock inChlamydomonas reinhardtii

1996

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The small gene family encoding the chlorophyll a/b-binding proteins of photosystem II (CABII or lhcb) is known to exhibit circadian rhythms of mRNA abundance in Chlamydomonas reinhardtii. In this study we investigated the role of transcription in the phenomenon. We used as reporters Chlamydomonas genes that encode nitrate reductase (NITI) and arylsulfatase (ARS2) transcriptionally fused to sequences upstream of one of the CABII genes (called CABII-1). We found that both reporters exhibited the same circadian rhythm of mRNA abundance in phase, period, and amplitude as does the endogenous CABII-1 gene. We also evaluated the efficacy of arylsulfatase enzymatic activity as a reporter and found that its half-life is too long to make it a useful reporter of rhythmic transcription during a circadian or diurnal cycle. The amount of mRNA synthesis from the CABII-1 gene was examined by in vivo labeling experiments and a circadian rhythm in transcription rate was demonstrated. In vivo labeling also revealed a circadian rhythm of mRNA synthesis for the CABII gene family as a whole. The results from the transcriptional reporter assays together with the in vivo labeling experiments strongly support the conclusion that the biological clock regulates the transcriptional activity of the CABII-I gene, and moreover that regulation at the transcriptional level is the predominant mode by which the clock regulates this gene.

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“…The distinction between diurnal and circadian rhythmicity requires the demonstration that oscillations persist under constant environmental conditions (for reviews on circadian rhythmicity see Bünning 1967 andSweeney 1987). Indeed, upon transfer to continuous light, oscillations continued, and the free running periodicity produced two maxima of sugar secretion (Fig.…”

Section: Resultsmentioning

confidence: 99%

Circadian rhythmicity of nectar secretion in Hoya carnosa

Matile¹

2006

Bot. Helv.

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Matile Ph. 2006. Circadian rhythmicity of nectar secretion in Hoya carnosa. Bot. Helv. 116: 1-7.A simple device for continuous sampling of nectar secreted in single flowers of Hoya carnosa R. Br. (Asclepiadaceae) is described. Sampling at 3 hrs intervals over several days revealed an oscillating secretion with maxima around midnight. Plants were transferred from a 12:12 hrs photoperiod to continuous illumination in order to distinguish between diurnal and circadian regulation. Under conditions of continuous illumination oscillations prevailed for two cycles and the free running period was about 29 hrs. Upon transfer to an inverted photoperiod, oscillations were immediately resumed and the maxima were entrained as to fall into the dark period. It is concluded that the rhythmicity of nectar secretion in H. carnosa is a manifestation of the biological clock.

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The Physiological Clock

Cited by 202 publications

References 0 publications

Circadian basis for the photoperiodic response in the male blackheaded bunting (Emberiza melanocephala)

Circadian basis for the photoperiodic response in the male blackheaded bunting (Emberiza melanocephala)

Transcription ofCABII is regulated by the biological clock inChlamydomonas reinhardtii

Circadian rhythmicity of nectar secretion in Hoya carnosa

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