The Initiation of an Endogenous Rhythm Affecting Flower Bud Formation in <i>Pharbitis nil</i>

Paraska, John R.; Spector, Calvin

doi:10.1111/j.1399-3054.1974.tb03727.x

Cited by 12 publications

(10 citation statements)

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“…One rhythm has a period of about 24 h (circadian), and it is most sensitive to rephasing by the lighton signal (11). The second rhythm has a period of about 12 h (hence semidian), and it is most sensitive to rephasing by the light-off signal (3,4).…”

Section: Maturity Genotypes Of the Milo Type Of Sorghum Bicolor (L)mentioning

confidence: 99%

Genetic Regulation of Development in Sorghum bicolor

Morgan

Guy²,

Pao³

1987

Plant Physiol.

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Asynchronous thermo-and photoperiods were observed to hasten floral differentiation (initiation) in the short day plant Sorghum bicolor (L.) Moench. Shifting the 12 hour thermoperiod forward 0.5 or 2.5 hours hastened floral initiation compared to controls with synchronous thermoand photoperiods. Delaying the day-night temperature change until 2.5 hours after either the dark-light or light-dark transition also hastened floral initiation. Inasmuch as sorghum milo-type maturity genotypes containing the genes designated MalMa2 (class I) were most responsive to asynchrony of the thermo-and photoperiods while those containing ma3 (class III) were not responsive, the maturity genes appear to control the plant's response to both photoperiod and temperature. Gibberellic acid promoted the effect of thermo-and photoperiod asynchrony on floral initiation. The results suggest that in sorghum both temperature and photoperiod may act as phase setting signals in what has previously been termed photoperiodism.Sorghum is a quantitative short day grass of tropical origin (12,14). Flowering is hastened by FR at the end of the light period (5, 20); phytochrome has been implicated in this response (5). GA3 also hastens floral differentiation (initiation) (20), but floral development is not hastened in such plants grown in the field under unfavorable photoperiods (PW Morgan, JR Quinby, unpublished data). In the milo variety of sorghum three genes which modify photoperiod requirements have mutated alleles; the alleles of these genes are designated Mal, mal, Ma2, ma2, Ma3, ma3, and ma3'. Eleven maturity genotypes, near isogenic except for the variations at the first three maturity loci, have been produced (12, 13) through appropriate breeding and selection. The most dramatic effects on photoperiodic behavior result from dominant genes at the first two loci (Ma1Ma2) or the ma3R allele at the third locus (10).The sensitivity of photoperiodic control of flowering to temperature was noted early by Quinby and Karper (14) sorghum (1, 15, 16), but their studies focused on the temperature level or the difference between day and night temperatures. The failure of some of the milo maturity genotypes to exhibit floral differentiation in the same sequence in the growth room as in the field has been noted (10, 20) and proposed to be due to temperature differences in the environments.A chance observation in our laboratory made us aware that the timing of the thermoperiod cycle relative to its synchrony with the photoperiod had a significant effect on the duration of growth prior to floral differentiation. We report here results of the ensuing investigation of effects ofthermoperiod/photoperiod synchrony on flower initiation in sorghum lines with genetically identified mutations affecting photoperiod requirements. MATERIALS AND METHODS Maturity genotypes of the milo type of Sorghum bicolor (L.)Moench were used as test plants. Seeds Culture of plants was as previously described in walk-in controlled environment rooms with 12 h light 12 h dark...

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Section: Maturity Genotypes Of the Milo Type Of Sorghum Bicolor (L)mentioning

confidence: 99%

Genetic Regulation of Development in Sorghum bicolor

Morgan

Guy²,

Pao³

1987

Plant Physiol.

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“…at the time of the light-off signal, and not by the preceding light-on signal as is apparently the case for the circadian rhythm analyzed by Paraska and Spector (14).…”

Section: Abstract?mentioning

confidence: 94%

“…If the circadian rhythm affecting the flowering response and initiated by the light-on signal (14) was also operative under our experimental conditions, we should expect to see some evidence ofinteraction between the two rhythms. Where they are in phase, the second peak (-14 h) and trough (-20 h) could be reduced in amplitude, as we have occasionally found.…”

Section: Discussionmentioning

confidence: 99%

“…However, the semidian rhythm appears to differ from the circadian one not only in its period length but possibly also in several other respects. First, whereas the phasing of the circadian rhythm appears to be set by a lighton signal ( 14), that ofthe semidian rhythm is set by the beginning of an interruption by FR or darkness, i.e. by a light-off signal (2).…”

Section: Discussionmentioning

confidence: 99%

“…Spector and Paraska (15) presented evidence for a circadian rhythm affecting flowering response in Pharbitis seedlings, which they subsequently (14) response. Lumsden et al (9) found that the rhythmic response to an R interruption of an inductive dark period was influenced, in its phasing, by the preceding light treatment and concluded that flowering in Pharbitis was controlled by a single circadian rhythm initiated by a light-on signal.…”

Section: Abstract?mentioning

confidence: 99%

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A Semidian Rhythm in the Flowering Response of Pharbitis nil to Far-Red Light

Heide¹,

King²,

Evans³

1986

Plant Physiol.

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ABSTRACT?Evidence is presented of an endogenous rhythm in flowering response to far-red (FR) irradiation, with a period of about 12 h (hence semidian rhythm), which persists through at least three cycles in constant conditions of continuous light at 27°C and has a marked influence on the flowering response in Pharbitis nil to a subsequent inductive dark period. The phase of the rhythm is not influenced by real time nor by the time from imbibition or from the beginning of the light period. Rather, it is fed forward from the beginning of the FR interruption to the beginning of the inductive dark period. The period of the rhythm is not affected by irradiance but is longer at cooler temperature. When there are two FR interruptions during the preceding light period, it is primarily the later one which determines the phase of the rhythm, although some interactions are evident. There appears to be an abrupt rephasing of the rhythm at the beginning of the inductive dark period. No overt rhythms which could be used as "clock hands" for the semidian rhythm were detected in photosynthesis, stomatal opening, or translocation.Although the effects ofR2 and FR interruptions during a single inductive dark period on flowering in Pharbitis nil Chois. seedlings have been widely examined (16,18), less attention has been given to the effect of R and FR interruptions of light preceding the inductive dark period.

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Effect of Aging on Growth and Flowering of the Terminal Bud of Pharbitis Nil

Owens

Paolillo

1986

American J of Botany

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The tendency of the terminal bud of Pharbitis nil to flower after one long night was studied in the context of growth changes occurring with aging. Seedlings were grown under constant light and temperature, selected for uniformity and subjected to a 16‐hr dark period at ages ranging from 3 to 14 days. A decline in percent terminals flowering was observed after day 6, to zero at day 10. Flowering of the terminal was obtained in some plants, thereafter. Floral index of development scored lower for terminals flowering on days 7–9 and 11–14 than on days 3–6. Loss of the tendency to flower was associated with a decline in rate of leaf production in the terminal bud and a change in rate of elongation of the epicotyl axis. The data lend support to a nutrient‐diversion hypothesis in the control of flowering in Pharbitis.

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The Initiation of an Endogenous Rhythm Affecting Flower Bud Formation in Pharbitis nil

Cited by 12 publications

References 3 publications

Genetic Regulation of Development in Sorghum bicolor

Genetic Regulation of Development in Sorghum bicolor

A Semidian Rhythm in the Flowering Response of Pharbitis nil to Far-Red Light

Effect of Aging on Growth and Flowering of the Terminal Bud of Pharbitis Nil

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