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H. Elliott Albers - One of the best experts on this subject based on the ideXlab platform.
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Effect of Photoperiod on vasopressin-induced aggression in Syrian hamsters.
Hormones and behavior, 2004Co-Authors: Heather K. Caldwell, H. Elliott AlbersAbstract:Syrian hamsters are Photoperiodic and become sexually quiescent when exposed to short "winter-like" Photoperiods. In short Photoperiods, male hamsters display significantly higher levels of aggression than males housed in long Photoperiods. Arginine-vasopressin (AVP) within the anterior hypothalamus (AH) has been reported to modulate aggression in hamsters housed in long Photoperiods. Previous studies have shown that AVP can facilitate aggression and its effects appear to be mediated by AVP V(1a) receptors (V(1a)R). In the present study, we investigated whether the increased levels of aggression observed after exposure to short Photoperiod were the result of an increased responsiveness to AVP within the AH. Injections of AVP into the AH significantly increased aggression in hamsters housed in a long Photoperiod, but had no effect in hamsters housed in a short Photoperiod. In addition, injection of a V(1a)R antagonist into the AH significantly inhibited aggression in hamsters housed in long Photoperiod, but had no effect in hamsters housed in a short Photoperiod. These findings indicate that AVP within the AH increases aggression in hamsters housed in long Photoperiods, but not in hamsters housed in short Photoperiods.
Richard A. Richards - One of the best experts on this subject based on the ideXlab platform.
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Responses of Leaf and Tiller Emergence and Primordium Initiation in Wheat and Barley to Interchanged Photoperiod
Annals of Botany, 2000Co-Authors: D. J. Miralles, Richard A. RichardsAbstract:Abstract The influence of constant (9, 13 and 19 h) and reciprocally-interchanged Photoperiods [at terminal spikelet (TS) or triple mound (TM)] on leaf, tiller and primordium development were examined using Photoperiod-responsive cultivars of spring wheat, ‘UQ 189’ and spring barley, ‘Arapiles’. In both species, constant longer Photoperiod reduced the duration from sowing (S) to double ridge (DR), as expected. However, Photoperiod sensitivity was not restricted to this mainly vegetative phase. There was also a marked increase or reduction in the duration of reproductive phases between TS/TM and heading (H) when plants were transferred to shorter or longer Photoperiods respectively, compared with controls. These responses were largely independent of the Photoperiod during previous phases although minor effects of the previous Photoperiod were observed. For both species, the time course of leaf emergence was linear, or bi-linear, depending on the final leaf number on the main stem. The rate of leaf emergence was faster for the first six to eight leaves than for the leaves appearing subsequently. The rate of emergence of early-formed leaves was independent of Photoperiod whereas the rate of emergence of later leaves varied with Photoperiod. Photoperiod also affected the dynamics of tillering. The rate of leaf primordium initiation was little affected by variation in Photoperiod, but the rate of spikelet initiation increased with increases in Photoperiod. The rates of leaf and spikelet primordium initiation were both substantially higher in barley than in wheat. The fact that the reproductive phase from TS/TM to H was largely independent of the duration of the previous phase provides evidence that this phase might be genetically manipulated to increase the time for floret development and hence grain number.
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Effects of high temperature and Photoperiod on floral development in wheat isolines differing in vernalisation and Photoperiod genes
Field Crops Research, 1993Co-Authors: H.m. Rawson, Richard A. RichardsAbstract:Abstract This paper examines whether high temperature modifies the effects of Photoperiod on reproductive development in six Triple Dirk isolines. Isolines chosen for study were genetically diverse in their responses to vernalisation and Photoperiod. The information is important when attempting to predict the performance of temperate wheats in high temperature locations such as the tropics. Averaged across isolines, days to ear emergence was reduced by 12 days for every hour that Photoperiod lengthened between 9 and 13 h in both 15 and 25°C mean temperature regimes, but responses amongst isolines differed. In day-degree terms, heading was delayed by high temperature in all isolines under all Photoperiods. In four of the lines, the delay to heading due to high temperature increased as Photoperiod shortened. This interaction resulted in similar calendar days to heading at 15 and 25°C under a 9-h Photoperiod. Heading date gave no insight into the timing of earlier phenological events. In general, high temperature delayed the appearance of double ridges under short Photoperiods in calendar day terms, but accelerated later development up to ear emergence. Conversely, high temperature shortened the time to double ridges under long Photoperiods. At moderate temperature (15°C), delays in the time of appearance of double ridges, associated both with shortening of Photoperiod and with genotype, led to the initiation of more spikelet primordia. By contrast, at high temperature (25°C), extended delays to double-ridge appearance resulted in little or no increase in spikelet primordia, as primordium production on the apex slowed and eventually ceased in some isolines. A retardation in primordium initiation was not reflected in leaf emergency rates. Consequently, the plastochron interval, expressed in day-degree terms, was affected far more by high temperature than the phyllochron interval.
Mark Stitt - One of the best experts on this subject based on the ideXlab platform.
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Photosynthate partitioning to starch in Arabidopsis thaliana is insensitive to light intensity but sensitive to Photoperiod due to a restriction on growth in the light in short Photoperiods.
Plant cell & environment, 2017Co-Authors: Virginie Mengin, Ronan Sulpice, Eva-theresa Pyl, Thiago Alexandre Moraes, Nicole Krohn, Beatrice Encke, Mark StittAbstract:Photoperiod duration can be predicted from previous days, but irradiance fluctuates in an unpredictable manner. To investigate how allocation to starch responds to changes in these two environmental variables, Arabidopsis Col-0 was grown in a 6 h and a 12 h Photoperiod at three different irradiances. The absolute rate of starch accumulation increased when Photoperiod duration was shortened and when irradiance was increased. The proportion of photosynthate allocated to starch increased strongly when Photoperiod duration was decreased but only slightly when irradiance was decreased. There was a small increase in the daytime level of sucrose and twofold increases in glucose, fructose and glucose 6-phosphate at a given irradiance in short Photoperiods compared to long Photoperiods. The rate of starch accumulation correlated strongly with sucrose and glucose levels in the light, irrespective of whether these sugars were responding to a change in Photoperiod or irradiance. Whole plant carbon budget modelling revealed a selective restriction of growth in the light period in short Photoperiods. It is proposed that Photoperiod sensing, possibly related to the duration of the night, restricts growth in the light period in short Photoperiods, increasing allocation to starch and providing more carbon reserves to support metabolism and growth in the long night.
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A long Photoperiod relaxes energy management in [i]Arabidopsis[/i] leaf six
Current Plant Biology, 2015Co-Authors: Katja Baerenfaller, Doris Russenberger, Ronan Sulpice, Lars Hennig, Mark Stitt, Sean Walsh, Catherine Massonnet, Christine Granier, Wilhelm GruissemAbstract:Plants adapt to the prevailing Photoperiod by adjusting growth and flowering to the availability of energy. To understand the molecular changes involved in adaptation to a long-day condition we comprehensively profiled leaf six at the end of the day and the end of the night at four developmental stages on Arabidopsis thaliana plants grown in a 16 h Photoperiod, and compared the profiles to those from leaf 6 of plants grown in a 8 h Photoperiod. When Arabidopsis is grown in a long-day Photoperiod individual leaf growth is accelerated but whole plant leaf area is decreased because total number of rosette leaves is restricted by the rapid transition to flowering. Carbohydrate measurements in long- and short-day Photoperiods revealed that a long Photoperiod decreases the extent of diurnal turnover of carbon reserves at all leaf stages. At the transcript level we found that the long-day condition has significantly reduced diurnal transcript level changes than in short-day condition, and that some transcripts shift their diurnal expression pattern. Functional categorisation of the transcripts with significantly different levels in short and long day conditions revealed Photoperiod-dependent differences in RNA processing and light and hormone signalling, increased abundance of transcripts for biotic stress response and flavonoid metabolism in long Photoperiods, and for photosynthesis and sugar transport in short Photoperiods. Furthermore, we found transcript level changes consistent with an early release of flowering repression in the long-day condition. Differences in protein levels between long and short Photoperiods mainly reflect an adjustment to the faster growth in long Photoperiods. In summary, the observed differences in the molecular profiles of leaf six grown in long- and short-day Photoperiods reveal changes in the regulation of metabolism that allow plants to adjust their metabolism to the available light. The data also suggest that energy management is in the two Photoperiods fundamentally different as a consequence of Photoperiod-dependent energy constraints.
Heather K. Caldwell - One of the best experts on this subject based on the ideXlab platform.
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Effect of Photoperiod on vasopressin-induced aggression in Syrian hamsters.
Hormones and behavior, 2004Co-Authors: Heather K. Caldwell, H. Elliott AlbersAbstract:Syrian hamsters are Photoperiodic and become sexually quiescent when exposed to short "winter-like" Photoperiods. In short Photoperiods, male hamsters display significantly higher levels of aggression than males housed in long Photoperiods. Arginine-vasopressin (AVP) within the anterior hypothalamus (AH) has been reported to modulate aggression in hamsters housed in long Photoperiods. Previous studies have shown that AVP can facilitate aggression and its effects appear to be mediated by AVP V(1a) receptors (V(1a)R). In the present study, we investigated whether the increased levels of aggression observed after exposure to short Photoperiod were the result of an increased responsiveness to AVP within the AH. Injections of AVP into the AH significantly increased aggression in hamsters housed in a long Photoperiod, but had no effect in hamsters housed in a short Photoperiod. In addition, injection of a V(1a)R antagonist into the AH significantly inhibited aggression in hamsters housed in long Photoperiod, but had no effect in hamsters housed in a short Photoperiod. These findings indicate that AVP within the AH increases aggression in hamsters housed in long Photoperiods, but not in hamsters housed in short Photoperiods.
Paul D. Heideman - One of the best experts on this subject based on the ideXlab platform.
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Reduced body mass, food intake, and testis size in response to short Photoperiod in adult F344 rats.
BMC physiology, 2002Co-Authors: M. Benjamin Shoemaker, Paul D. HeidemanAbstract:Although laboratory rats are often considered classic nonseasonal breeders, peripubertal rats of two inbred strains, F344 and BN, have both reproductive and nonreproductive responses to short Photoperiods. Unmanipulated adult rats have not been reported to have robust responses to short Photoperiod alone, although several treatments can induce Photoperiodic responses in adults. In this study, we tested the hypotheses that unmanipulated F344 rats retain responses to short Photoperiod as adults and that they have the necessary elements for an endogenous circannual rhythm of sensitivity to short Photoperiod. Relative to rats kept in long Photoperiods (L16:D8), adult F344 rats transferred at 4.5 months of age to short Photoperiods (L8:D16) had significantly lower testis size, food intake, and body weight. In a second experiment, newly weaned F344 rats underwent an initial period of inhibition of reproductive maturation, lower food intake, and lower body weight in short Photoperiod or intermediate Photoperiod (L12:D12) relative to rats in long Photoperiod. By 18 weeks of treatment, rats in the two inhibitory Photoperiods no longer differed from long Photoperiod controls. In short Photoperiod, rats underwent a second period of slight reproductive inhibition between weeks 35 and 48, but there was an effect on body weight and slight inhibition of food intake only in an intermediate Photoperiod. Male F344 rats retain photoresponsiveness as adults, with less reproductive inhibition but equivalent nonreproductive responses. There was only weak evidence for an endogenous timer controlling a circannual cycle of sensitivity to short Photoperiod.
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Inhibition of Reproductive Maturation and Somatic Growth of Fischer 344 Rats by Photoperiods Shorter than L14:D10 and by Gradually Decreasing Photoperiod
Biology of reproduction, 2000Co-Authors: Paul D. Heideman, Cynthia K. Bierl, M. Eric GalvezAbstract:Photoperiod is the major regulator of reproduction in temperate-zone mammals. Laboratory rats are generally considered to be nonphotoresponsive, but young male Fischer 344 (F344) rats have a uniquely robust response to short Photoperiods of 8 h of light. Rats transferred at weaning from a Photoperiod of 16 h to Photoperiods of < 14 h of light slowed in both reproductive development and somatic growth rate. Those in Photoperiods < 13 h of light underwent the strongest responses. The critical Photoperiod of F344 rats can be defined as 13.5 h of light, but Photoperiods of
