Evidence that photoperiodic, dark time measurement in <i>Pharbitis nil</i> involves a circadian rather than a semidian rhythm

Lumsden, P. J.; Youngs, Jennifer; Thomas, Brian; Vince‐Prue, Daphne

doi:10.1111/j.1365-3040.1995.tb00201.x

Cited by 7 publications

(5 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The circadian rhythm that controls flowering was measured by the repression of flowering in response to a 'night-break' light pulse (Figure 1). The time of maximum repression (NBmax) was completely determined by the time of the transfer to darkness, as other authors have shown (Lumsden et al, 1995;Thomas and Vince-Prue, 1997 and references therein). However, the peak times of output rhythms that peak in the day, such as transpiration rate and LHCB RNA levels, were little affected by the transition to darkness (Figure 1), instead retaining a similar peak time relative to the start of the light interval.…”

Section: Resultsmentioning

confidence: 81%

“…Seeds of I. nil ( Pharbitis nil ) Choisy cv. Violet were planted and grown as described ( Lumsden et al, 1995 ). Unless otherwise noted, all Arabidopsis seeds were sterilised and grown on solid media containing 3% sucrose, as described previously ( Edwards et al, 2005 ).…”

Section: Methodsmentioning

confidence: 99%

“…The method was essentially as described ( Lumsden et al, 1995 ). Seedlings were grown in continuous light, and, after durations of between 72 and 96 h, ‘released' into a dark period of 48 h. During the first 12 h of darkness, night breaks of 10 min red light were given at hourly intervals, to determine the time of maximal response to the night break.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Quantitative analysis of regulatory flexibility under changing environmental conditions

Edwards

Akman

Knox

et al. 2010

Molecular Systems Biology

103

151

View full text Add to dashboard Cite

Day length changes with the seasons in temperate latitudes, affecting the many biological rhythms that entrain to the day/night cycle: we measure these effects on the expression of Arabidopsis clock genes, using RNA and reporter gene readouts, with a new method of phase analysis.Dusk sensitivity is proposed as a simple, natural and general mathematical measure to analyse and manipulate the changing phase of a clock output relative to the change in the day/night cycle.Dusk sensitivity shows how increasing the numbers of feedback loops in the Arabidopsis clock models allows more flexible regulation, consistent with a previously-proposed, general operating principle of biological networks.The Arabidopsis clock genes show flexibility of regulation that is characteristic of a three-loop clock model, validating aspects of the model and the operating principle, but some clock output genes show greater flexibility arising from direct light regulation.

show abstract

Section: Resultsmentioning

confidence: 81%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Quantitative analysis of regulatory flexibility under changing environmental conditions

Edwards

Akman

Knox

et al. 2010

Molecular Systems Biology

103

151

View full text Add to dashboard Cite

show abstract

“…However, the total duration of light or darkness was not the critical factor determining the response in other plant and animal species. For example, when Japanese morning glory (Ipomea nil, also described as Pharbitis nil) were transferred to extended nights, appropriately timed night breaks mimicked the effects of long days and inhibited flowering (4). Remarkably, sensitivity to night breaks varied with a 24-hr period.…”

mentioning

confidence: 99%

Floral responses to photoperiod are correlated with the timing of rhythmic expression relative to dawn and dusk inArabidopsis

Roden

Song

Jackson

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

109

View full text Add to dashboard Cite

Daylength, or photoperiod, is perceived as a seasonal signal for the control of flowering of many plants. The measurement of daylength is thought to be mediated through the interaction of phototransduction pathways with a circadian rhythm, so that flowering is induced (in long-day plants) or repressed (in short-day plants) when light coincides with a sensitive phase of the circadian cycle. To test this hypothesis in the facultative long-day plant, Arabidopsis thaliana, we used varying, non-24-hr light͞dark cycles to alter the timing of circadian rhythms of gene expression relative to dawn and dusk. Effects on circadian rhythms were correlated with those on flowering times. We show that conditions that displaced subjective night events, such as expression of the flowering time regulator CONSTANS into the light portion of the cycle, were perceived as longer days. This work demonstrates that the perception of daylength in Arabidopsis relies on adjustments of the phase angle of circadian rhythms relative to the light͞dark cycle, rather than on the measurement of the absolute duration of light and darkness.T he sexual reproduction of many plants and animals occurs on a seasonal basis and is triggered by changes in daylength, or photoperiod. In plants, floral responses to photoperiod vary widely between species and have been classified into three broad categories. Short-day plants are induced to flower when the photoperiod is shorter than a critical daylength, whereas longday plants flower under photoperiods that are longer than their critical daylength; day-neutral plants are insensitive to photoperiod.Measurement of day-or night-length could, in theory, be performed by an hourglass-type of timer, measuring time from either dawn or dusk, or even the relative amounts of light and darkness. For example, flowering of cocklebur (Xanthium) is essentially determined by the absolute duration of darkness (1, 2), and induction of diapause in the aphid Megoura viciae relies on measuring time from dusk (3). However, the total duration of light or darkness was not the critical factor determining the response in other plant and animal species. For example, when Japanese morning glory (Ipomea nil, also described as Pharbitis nil) were transferred to extended nights, appropriately timed night breaks mimicked the effects of long days and inhibited flowering (4). Remarkably, sensitivity to night breaks varied with a 24-hr period. Gonadal development in birds and induction of diapause in insects also exhibited rhythmic responsiveness to short light signals in constant darkness (3, 5).These and other similar findings (reviewed in ref.2) suggested that photoperiodic time measurement may involve a circadian rhythm of responsiveness to light, known as the photoperiodic response rhythm (6). Two possible mechanisms have been proposed, by which a circadian clock might mediate perception of photoperiod (7). According to the external coincidence model, a photoperiodic response may be induced when an external signal (light) coincides with a pho...

show abstract

“…3). Hour 8 after the start of inductive dark period is when a night break is most effective in preventing flower induction, and an 8h dark period is shorter than the critical night length for P. nil (Lumsden et al 1995). This presumably indicates that ABA inhibited the time-measuring process, and not the production of the flowering stimulus.…”

Section: Organ Treatedmentioning

confidence: 99%

Abscisic acid both promotes and inhibits photoperiodic flowering of Pharbitis nil

Takeno

Maeda

1996

Physiologia Plantarum

View full text Add to dashboard Cite

Abscisic acid (ABA) has been reported to have diverse effects on photoperiodic flowering. Activity of a natural ABA, (+)‐(S)‐abscisic acid (S‐ABA), was recently suggested to be somewhat different from that of racemic ABA, which has been used in previous work. Use of S‐ABA might enable clarification of the role of ABA in flowering. S‐ABA inhibited flowering of the short‐day plant Pharbitis nil (cv. Violet) when given before or 4 h after the start of a 14‐h inductive dark period, and promoted flowering when given 12 h after the start of the dark period or later. The flower‐promoting effect was observed when ABA was applied to the shoot apex. These results indicate that ABA has a dual effect on photoperiodic flowering of P. nil: it may inhibit the time‐measuring process as well as promote some processes that proceed after generation of the flowering stimulus.

show abstract

Evidence that photoperiodic, dark time measurement in Pharbitis nil involves a circadian rather than a semidian rhythm

Cited by 7 publications

References 15 publications

Quantitative analysis of regulatory flexibility under changing environmental conditions

Quantitative analysis of regulatory flexibility under changing environmental conditions

Floral responses to photoperiod are correlated with the timing of rhythmic expression relative to dawn and dusk inArabidopsis

Abscisic acid both promotes and inhibits photoperiodic flowering of Pharbitis nil

Contact Info

Product

Resources

About