CIRCADIAN RHYTHMIC FLOWERING RESPONSES IN CHENOPODIUM RUBRUM: EFFECTS OF GLUCOSE AND SUCROSE

1967 ◽  
Vol 45 (11) ◽  
pp. 2173-2193 ◽  
Author(s):  
Bruce G. Cumming
Keyword(s):  
Continuous Light ◽  
Light Period ◽  
Chenopodium Rubrum ◽  
Measuring System ◽  
Inhibitory Effects ◽  
Measuring Time ◽  
Natural Conditions ◽  
Similar Time ◽  
Endogenous Circadian Rhythm ◽  
Free Running

An endogenous circadian rhythm of flower induction in Chenopodium rubrum that depends on the length of darkness interrupting continuous light has a smaller amplitude and damps out earlier when the light preceding and (or) following darkness is limited in intensity. Glucose or sucrose, fed to plants throughout darkness, can enhance and sustain the rhythm over a considerably longer period. Some degree of specificity of glucose in the rhythmic process was indicated because, when this energy source was applied during a skotophile phase of darkness (particularly the first 9 h) there were inhibitory effects on the rhythmic flowering response, but the same concentration of glucose was stimulatory when applied during the photophile phase(s) of darkness. No similar time dependence resulted from sucrose treatments. To account for the effects of glucose in particular, it is postulated that endogenous sugar formation in the light period is involved in providing substrate for phytochrome-Pfr action or mediation during darkness. Damping out of the oscillation in extended dark periods is a consequence of depletion of sugar reserves during darkness. These and other results support the concept that Pfr acts as a pacemaker or valve and exerts some control over sugar availability and utilization. Comparisons involving the application of glucose to different ecotypes suggest that, for optimal induction, some definite balance is required between the endogenous availability of glucose, or some other sugar derivative(s), and the level of phytochrome Pfr; this balance apparently differs according to genotype.Differences between ecotypes in their rhythmic flowering responses suggest that the endogenous free-running clock is an integral part of the time-measuring system in daily photoperiodic cycles and that it does have a role in measuring time under natural conditions.

RHYTHMIC FLOWERING RESPONSES AND PHYTOCHROME CHANGES IN A SELECTION OF CHENOPODIUM RUBRUM

1965 ◽  
Vol 43 (7) ◽  
pp. 825-853 ◽  
Author(s):  
Bruce G. Cumming ◽  
Sterling B. Hendricks ◽  
H. A. Borthwick
Keyword(s):  
Dark Period ◽  
Continuous Light ◽  
Endogenous Rhythm ◽  
Chenopodium Rubrum ◽  
Flowering Response ◽  
Initial Substrate ◽  
Endogenous Circadian Rhythm ◽  
Light Darkness ◽  
Rhythmic Change

Flowering of Chenopodium rubrum L., selection 374, was examined with respect to an endogenous circadian rhythm, the state of phytochrome, and the result of changing the form of phytochrome during a single dark period of 2 to 96 hours interrupting continuous light. Darkness was imposed either 4 or 5 days after seeds were placed on moist filter paper in Petri dishes.The following working hypothesis, which is partly retrospective, is projected to explain the main features of the experimental results. Flowering is controlled by a product of the enzymatic action of the far-red absorbing form of phytochrome (Pfr) on a single but unknown substrate. In acting, Pfr finally reverts to the inactive red-absorbing form of phytochrome (Pr) or is changed from the Pfr form in some other way. The available substrate, if not utilized by Pfr action, is soon depleted by other reactions. The substrate for Pfr action is low during the skotophile but high during the photophile phases. The significant time for phasing is the beginning of darkness. The initial substrate supply appears to be derived from the preceding light period but some time in the region of the 9th to 12th hour of darkness a significant rhythmic change of substrate starts up. The dependence of flowering on the time that darkness is interrupted by light is directly related to a rhythmic change in the optimum Pfr level required for the processes leading to flowering.The role of the endogenous rhythm in flowering under natural conditions is questioned. Similarities that are shown in the control of flowering, whether the display is governed by an endogenous rhythm or by a daily photoperiodic cycle, indicate that phytochrome acts as a "pacemaker". It is suggested that the distinct ecotypic populations of C. rubrum that differ in flowering response have dissimilar levels and rates of supply of substrate for phytochrome action. In C. rubrum-374, complete reversion or loss of Pfr does not occur during a long dark period of 72 hours at 20 °C, but Pfr does decrease to low levels.A hydrodynamic system is discussed as an analogy to rhythmic flowering response.

Restricted food access and light-dark: impact of conflicting zeitgebers on circadian rhythms of the rabbit

1993 ◽  
Vol 264 (4) ◽  
pp. R708-R715 ◽  
Author(s):  
B. Jilge ◽  
H. Stahle
Keyword(s):  
Circadian Rhythms ◽  
Phase Difference ◽  
Food Access ◽  
Activity Rhythm ◽  
Light Period ◽  
The Other ◽  
Behavioral Rhythms ◽  
Activity Component ◽  
Common Control ◽  
Free Running

Free-running circadian rhythms of rabbits were exposed to a 11:55-11:55-h light-dark (LD) schedule. After complete entrainment (63 +/- 22 days), the predominantly nocturnally active rabbits were exposed to an additional zeitgeber, restricted food access (RF), which was imposed during the light period. In five animals RF had the same period (T) as the LD cycle (23:50 h), and in five other animals TRF was 24:10 h. At a period of 23:50 h for both zeitgebers, the rhythms of four animals were stably entrained to RF, while in one animal a component of the rhythm broke away from RF and entrained to the LD zeitgeber. In animals exposed to zeitgebers of different periods most of the activity rhythm also entrained to RF, but 20 +/- 7% of the activity entrained to the LD zeitgeber. The light-entrained activity component merged with the RF component when the zeitgebers crossed, and decomposition occurred when the phase difference exceeded 4-6 h. The results indicate that two circadian oscillator systems exist in the rabbit, one entrained by light-dark cycles and the other by feeding-fasting cycles. Both exert common control over a number of overt behavioral rhythms.

Rhythms of larval release in the shore crab Carcinus maenas (Decapoda: Brachyura)

1997 ◽  
Vol 77 (2) ◽  
pp. 451-461 ◽  
Author(s):  
Chaoshu Zeng ◽  
Ernest Naylor
Keyword(s):  
High Tide ◽  
Carcinus Maenas ◽  
Continuous Light ◽  
Time Lapse ◽  
Shore Crab ◽  
Dark Phase ◽  
Larval Release ◽  
Natural Conditions ◽  
Video Recorder ◽  
The Times

The process of larval release in field collected ovigerous Carcinus maenas was monitored in the laboratory using a time-lapse video recorder. Under constant light (L:L) and simulated natural light/dark cycles (L:D), larval release normally occurred in two or more main events at about daily and/or tidal intervals. Since larval release in the crab was expressed with circadian and circatidal periodicity in continuous light and in the absence of tidal cues, it suggests involvement of endogenous timing. Crabs showing daily larval release rhythms released larvae at various times of the day in L:L. In contrast, under simulated L:D cycles, 37 out of 38 crabs released larvae during the dark phase, suggesting nocturnal release of larvae in the crab under natural conditions. Larval release from freshly collected females which shed larvae within two days of collection occurred predominantly around the times of expected nocturnal high tide. When both local semidiurnal high tides occurred in daylight during long summer days, larval release appeared to start 2–3 h earlier than the expected morning high tide, before the onset of daylight. Larval release at the time around high tide, linked to a previously described larval tidal migration rhythm of ebb-phased upward swimming, is likely to have been selected for by enhancing the larval offshore dispersal process. Nocturnal larval release is probably adaptive in the avoidance of visual predators by ovigerous females as they release larvae.

scholarly journals Photoperiodic modulation of circadian rhythms in the silk gland protein profiles of Bombyx mori and its influence on the silk productivity and quality

2010 ◽  
Vol 2 (1) ◽  
pp. 48-56 ◽  
Author(s):  
B. Sailaja ◽  
S. Sivaprasad
Keyword(s):  
Circadian Rhythms ◽  
Bombyx Mori ◽  
Continuous Light ◽  
Silk Gland ◽  
Protein Profiles ◽  
Dark Cycle ◽  
Response Curves ◽  
Silk Proteins ◽  
Free Running ◽  
Clock Shift

Circadian rhythms in the silk gland protein profiles of Bombyx mori were analyzed under 12 h light and 12 h dark cycle (LD), continuous light (LL) and continuous dark (DD) conditions. The phase response curves of protein rhythms indicate the prevalence of a series of silk cycles, each comprising three phases; transcription, translation and consolidation of silk proteins. In the 24h- protein rhythm, the silk cycle repeats every 3h, 42 m under LD, 2h, 36m under LL and 3h under DD. The light and dark conditions advanced the rhythm of each silk cycle by 48m and 24m respectively. As a result the silk gland completes 7 rounds of protein synthesis under LD, 9 rounds under LL and 8 rounds under DD during the 24h-free running time of the rhythm. The light-induced clock-shift in the protein rhythm caused significant gains in economic parameters of sericulture with positive signals for enhancing silk productivity and quality.

Seasonal changes in serum thyroid hormone levels in ruffed grouse maintained under natural conditions of temperature and photoperiod

1979 ◽  
Vol 57 (10) ◽  
pp. 2022-2027 ◽  
Author(s):  
A. Garbutt ◽  
J. F. Leatherland ◽  
A. L. A. Middleton
Keyword(s):  
Thyroid Hormone ◽  
Seasonal Changes ◽  
Gonadal Development ◽  
Early Spring ◽  
Light Period ◽  
Ruffed Grouse ◽  
Natural Conditions ◽  
Blood Samples ◽  
Serum Thyroid Hormone ◽  
Thyroid Hormone Levels

Serum triiodothyronine (T3) and thyroxine (T4) concentrations were measured in a population of ruffed grouse, held outdoors under natural conditions of photoperiod and temperature. Blood samples were collected at monthly intervals, and at the solstices and equinoxes to test for variation through the light period. No changes in T4 or T3 levels were found during the light period but levels of T3 and T4 showed marked seasonal changes. Lowest T4 and T3 levels were found in birds during the winter months, with an increase in the concentration of both hormones in early spring concomitant with gonadal development in the adults. A lowering of serum T4 and T3 values was associated with the period of molt.

Circadian rhythm and response to light of extracellular glutamate and aspartate in rat suprachiasmatic nucleus

1996 ◽  
Vol 271 (3) ◽  
pp. R579-R585 ◽  
Author(s):  
S. Honma ◽  
Y. Katsuno ◽  
K. Shinohara ◽  
H. Abe ◽  
K. Honma
Keyword(s):  
Circadian Rhythm ◽  
Suprachiasmatic Nucleus ◽  
Light Pulse ◽  
Continuous Light ◽  
In Vivo Microdialysis ◽  
Dark Phase ◽  
Dark Cycle ◽  
Complete Darkness ◽  
Endogenous Circadian Rhythm

Extracellular concentrations of glutamate and aspartate were measured in the vicinity of rat suprachiasmatic nucleus (SCN) by means of in vivo microdialysis. The concentrations of both excitatory amino acids (EAAs) were higher during the dark phase than during the light under the light-dark cycle, showing pulsatile fluctuations throughout the day. When rats were released into the complete darkness, the 24-h pattern in the aspartate continued for at least one cycle, whereas that in the glutamate disappeared. The nocturnal increases in the EAA levels were not due to the increase of locomotor activity during the nighttime, because the 24-h rhythms were also detected in animals under urethan anesthesia. The patterns of extracellular EAA levels were changed when rats were released into the continuous light. Circadian rhythm was not detected in the glutamate, whereas the 24-h pattern was maintained in the aspartate with the levels increased to various extents. A 30-min light pulse given either at zeitgber time (ZT) 1 or ZT 13 elevated the EAA levels during the latter half of the light pulse, except glutamate by a pulse at ZT 1. The extracellular EAA levels in the vicinity of the rat SCN showed the circadian rhythm with a nocturnal peak and increased in response to the continuous light and a brief light pulse. The aspartate level is considered to be regulated by the endogenous circadian rhythm, but the glutamate levels seems to be modified by the light-dark cycle.

Splitting of the locomotor activity rhythm in rats by exposure to continuous light

1983 ◽  
Vol 244 (4) ◽  
pp. R573-R576 ◽  
Author(s):  
Phyllis W. Cheung ◽  
Charles E. McCormack
Keyword(s):  
Locomotor Activity ◽  
Estrous Cycle ◽  
Activity Rhythm ◽  
Continuous Light ◽  
Female Rats ◽  
Locomotor Rhythm ◽  
Estrous Cycles ◽  
Locomotor Activity Rhythm ◽  
Active Portion ◽  
Free Running

Female rats exposed to low intensities (0.1–1.5 lx) of continuous light (LL), displayed regular estrous cycles and free-running circadian rhythms of locomotor activity. In most rats, as the intensity of LL was increased to >2.0 lx, components within the active portion (α) of the locomotor rhythm remained synchronized as the periodicity of the rhythm lengthened. However, in a few rats agr split into two components; one of which free-ran with a period shorter than 24 h, while the other free-ran with a period longer than 24 h. As soon as the two components became maximally separated they spontaneously rejoined. In most rats, estrous cycles ceased shortly after the intensity of LL was increased to >2.0 lx even though the locomotor activity rhythm retained its unsplit free-running nature. These observations suggest that the multiple oscillators that control the rhythms of locomotor activity and the estrous cycle are normally coupled to one another. In certain intensities of LL, these oscillators uncouple and free-run with different periodicities, a condition which causes estrous cycles to cease and sometimes produces a split locomotor activity rhythm. circadian rhythm; oscillators; estrous cycle Submitted on November 9, 1981 Accepted on October 11, 1982

Internal synchronization among several circadian rhythms in rats under constant light

1978 ◽  
Vol 235 (5) ◽  
pp. R243-R249 ◽  
Author(s):  
K. I. Honma ◽  
T. Hiroshige
Keyword(s):  
Locomotor Activity ◽  
Body Temperature ◽  
Circadian Rhythms ◽  
Continuous Light ◽  
Biological Rhythms ◽  
Plasma Corticosterone ◽  
Dark Cycle ◽  
Internal Oscillator ◽  
Free Running ◽  
Phase Angles

Three biological rhythms (locomotor activity, body temperature, and plasma corticosterone) were measured simultaneously in individual rats under light-dark cycles and continuous light. Spontaneous locomotor activity was recorded on an Animex and body temperature was telemetrically monitored throughout the experiments. Blood samples were obtained serially at 2-h intervals on the experimental days. Phase angles of these rhythms were calculated by a least-squares spectrum analysis. Under light-dark cycles, the acrophases of locomotor activity, body temperature, and plasma corticosterone were found at 0029, 0106, and 1940 h, respectively. When rats were exposed to 200 lx continuous light, locomotor activity and body temperature showed free-running rhythms with a period of 25.2 h on the average. Plasma corticosterone levels determined at 12 days after exposure to continuous light exhibited a circadian rhythm with the acrophase shifted to 0720. The acrophases of locomotor activity and body temperature, determined simultaneously on the same day, were found to be located at 1303 and 1358 h, respectively. Phase-angle differences among the three rhythms on the 12th day of continuous light were essentially the same with those under the light-dark cycle. These results suggest that circadian rhythms of locomotor activity, body temperature, and plasma corticosterone are most probably coupled to a common internal oscillator in the rat.

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