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‣ Variações interanuais na fenologia de uma comunidade arbórea de floresta semidecídua no sudeste do Brasil

Rubim, Paulo; Nascimento, Henrique E. M.; Morellato, Leonor Patrícia C.
Fonte: Sociedade Botânica do Brasil Publicador: Sociedade Botânica do Brasil
Tipo: Artigo de Revista Científica Formato: 756-762
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); As comunidades arbóreas de florestas tropicais localizadas em regiões com clima sazonal tendem a ajustar a fenologia da queda de folhas e da produção de flores e frutos à sazonalidade climática. Neste estudo monitoramos a comunidade arbórea de uma floresta semidecidual no período de quatro anos (2001 a 2004), a fim de analisar a relação entre o número de espécies perdendo folhas, florescendo e frutificando e a variação anual do comprimento do dia, precipitação e temperatura durante o período de observação. Além disso, avaliamos se essas três fenofases repetem os mesmos padrões em anos sucessivos. Regressões lineares simples indicaram que o número de espécies perdendo folhas foi negativamente relacionado com as três variáveis ambientais para os quatro anos de estudo, sendo o comprimento do dia e a temperatura os melhores preditores para esta fenofase. Houve também relação significativa do comprimento do dia com o número de espécies florescendo e frutificando nos quatro anos, porém, precipitação e temperatura não foram relacionadas com estas fenofases em todos os anos de estudo. Os testes de estatística circular indicaram forte sazonalidade para queda foliar...

‣ Environmental drivers of leaf phenology in trees of the tropical species Ficus obtusifolia

Ballestrini,Caín; Tezara,Wilmer; Herrera,Ana
Fonte: Brazilian Journal of Plant Physiology Publicador: Brazilian Journal of Plant Physiology
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 Português
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Vegetative as well as reproductive phenology of tropical trees frequently occur synchronously at the end of the dry season. It has been repeatedly observed on two individuals of the tropical species Ficus obtusifolia growing in Caracas that they lose their entire foliage in a period of 48 h during the dry season and renew it within the next 72 h. In order to gain knowledge on the mechanisms that govern leaf exchange in F. obtusifolia, we followed in these two individuals the seasonal changes in leaf and fruit phenology, water relations and environmental variables, and in another 25, phenology only. Although foliar exchange was always observed before the rainy season, it also occurred near the end of the rainy season. An increase in leaf turgor potential of mature leaves and a low sap flow velocity coincided with leaf fall. Foliar exchange in all 27 individuals, growing in locations with different elevation and, possibly, access to underground water, was bi-modal and occurred in a period of approximately one month around both equinoxes. The presence of fruits was also bi-modal, occurring after leaf renewal. The sequence of phenological events repeated itself in all the individuals studied, although with inter-annual and individual variations in date of foliar exchange. Leaf fall was independent of leaf water status and significantly correlated with...

‣ Pea Mutants with Reduced Sensitivity to Far-Red Light Define an Important Role for Phytochrome A in Day-Length Detection.

Weller, J. L.; Murfet, I. C.; Reid, J. B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1997 Português
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In garden pea (Pisum sativum L.), a long-day plant, long photoperiods promote flowering by reducing the synthesis or transport of a graft-transmissible inhibitor of flowering. Previous physiological studies have indicated that this promotive effect is predominantly achieved through a response that requires long exposures to light and for which far-red (FR) light is the most effective. These characteristics implicate the action of phytochrome A (phyA). To investigate this matter further, we screened ethylmethane sulfonate-mutagenized pea seedlings for FR-unresponsive, potentially phyA-deficient mutants. Two allelic, recessive mutants were isolated and were designated fun1 for FR unresponsive. The fun1-1 mutant is specifically deficient in the PHYA apoprotein and has a seedling phenotype indistinguishable from wild type when grown under white light. However, fun1-1 plants grown to maturity under long photoperiods show a highly pleiotropic phenotype, with short internodes, thickened stems, delayed flowering and senescence, longer peduncles, and higher seed yield. This phenotype results in large part from an inability of fun1-1 to detect day extensions. These results establish a crucial role for phyA in the control of flowering in pea...

‣ Day length and estradiol affect same-sex affiliative behavior in the female meadow vole

Beery, Annaliese K.; Loo, Theresa J.; Zucker, Irving
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Non-sexual social bonding between adult mammals remains poorly understood, despite its importance in many species. Female meadow voles are territorial and nest alone in long summer day lengths when circulating estradiol concentrations are high, but cohabit in groups in short winter photoperiods when estradiol secretion is low. The influence of day length and estradiol on same-sex huddling behavior was assessed in adult female pairs housed together in long day lengths (LDs) or short day lengths (SDs) from weaning. The behavior of intact, ovariectomized, and estradiol-treated ovariectomized females from each photoperiod was assessed during 3 hour partner preference tests. Intact SD voles, unlike intact LD voles, spent the majority of the test in proximity to their cage mates. Estradiol treatment of SD voles significantly reduced time spent huddling with the partner. Neither ovariectomy nor estradiol treatment significantly affected the amount of time LD females spent in contact with their partners. Low estradiol availability is therefore a necessary but not sufficient condition for maintenance of high levels of huddling. These results establish that ovarian hormones interact with photoperiod to affect same-sex social behavior.

‣ Day-length Encoding Through Tonic Photic Effects in the Retinorecipient SCN Region

Yan, Lily; Silver, Rae
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/2008 Português
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The circadian clock in the suprachiasmatic nucleus (SCN) plays a critical role in seasonal processes by sensing ambient photoperiod. To explore how it measures daylength, we assessed the state of SCN oscillators using markers for neuronal activity (c-FOS) and the clock protein (PER1) in Syrian hamsters housed in long (LD, 16:8hr light:dark) versus short days (SD, 8:16hr light:dark). During SD, there was no detectable phase dispersion across the rostro-caudal extent of the nucleus. In contrast, during LD, rhythms in the caudal SCN phase led those in the mid- and rostral SCN by 4–8 h and 8–12 h, respectively. Importantly, some neurons in the retinorecipient core SCN were unique in that they were FOS-positive during the dark phase in LD, but not SD. Transfer of LD animals to constant darkness or skeleton photoperiod revealed that dark phase FOS expression depends on tonic light exposure rather than on intrinsic clock properties. By transferring animals from SD to LD, we next discovered that there are two separate populations of SCN cells one responding to acute and the other to tonic light exposure. The results suggest that the SCN’s seasonal encoding of day-length entails reorganization of its constituent oscillators by a subgroup of neurons in the SCN core that respond to tonic photic cues.

‣ Expression analysis of vernalization and day-length response genes in barley (Hordeum vulgare L.) indicates that VRNH2 is a repressor of PPDH2 (HvFT3) under long days

Casao, M. Cristina; Igartua, Ernesto; Karsai, Ildiko; Lasa, José Manuel; Gracia, M. Pilar; Casas, Ana M.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
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The response to vernalization and the expression of genes associated with responses to vernalization (VRNH1, VRNH2, and VRNH3) and photoperiod (PPDH1 and PPDH2) were analysed in four barley (Hordeum vulgare L.) lines: ‘Alexis’ (spring), ‘Plaisant’ (winter), SBCC058, and SBCC106 (Spanish inbred lines), grown under conditions of vernalization and short days (VSD) or no vernalization and long days (NVLD). The four genotypes differ in VRNH1. Their growth habits and responses to vernalization correlated with the level of expression of VRNH1 and the length of intron 1. ‘Alexis’ and ‘Plaisant’ behaved as expected. SBCC058 and SBCC106 showed an intermediate growth habit and flowered relatively late in the absence of vernalization. VRNH1 expression was induced by cold for all genotypes. Under VSD, VRNH1 expression was detected in the SBCC genotypes later than in ‘Alexis’ but earlier than in ‘Plaisant’. VRNH2 was repressed under short days while VRNH1 expression increased in parallel. VRNH3 was detected only in ‘Alexis’ under NVLD, whereas it was not expressed in plants with the active allele of VRNH2 (SBCC058 and ‘Plaisant’). Under VSD, PPDH2 was expressed in ‘Alexis’, SBCC058, and SBCC106, but it was only expressed weakly in ‘Alexis’ under NVLD. Further analysis of PPDH2 expression in two barley doubled haploid populations revealed that...

‣ Variation in hippocampal morphology along an environmental gradient: controlling for the effects of day length

Roth, Timothy C.; LaDage, Lara D.; Pravosudov, Vladimir V.
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
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Environmental conditions may create increased demands for memory, which in turn may affect specific brain regions responsible for memory function. This may occur either via phenotypic plasticity or selection for individuals with enhanced cognitive abilities. For food-caching animals, in particular, spatial memory appears to be important because it may have a direct effect on fitness via their ability to accurately retrieve food caches. Our previous studies have shown that caching animals living in more harsh environments (characterized by low temperatures, high snow cover and short day lengths) possess more neurons within a larger hippocampus (Hp), a part of the brain involved in spatial memory. However, the relative role of each of these environmental features in the relationship is unknown. Here, we dissociate the effects of one theoretically important factor (day length) within the environmental severity/Hp relationship by examining food-caching birds (black-capped chickadee, Poecile atricapillus) selected at locations along the same latitude, but with very different climatic regimes. There was a significant difference in Hp attributes among populations along the same latitude with very different climatic features. Birds from the climatically mild location had significantly smaller Hp volumes and fewer Hp neurons than birds from the more harsh populations...

‣ Estimation of Effective Day Length at Any Light Intensity Using Solar Radiation Data

Yokoya, Masana; Shimizu, Hideyasu
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Português
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The influence of day length on living creatures differs with the photosensitivity of the creature; however, the possible sunshine duration (N0) might be an inadequate index of the photoperiod for creatures with low light sensitivity. To address this issue, the authors tried to estimate the effective day length, i.e., the duration of the photoperiod that exceeds a certain threshold of light intensity. Continual global solar radiation observation data were gathered from the baseline surface radiation network (BSRN) of 18 sites from 2004 to 2007 and were converted to illuminance data using a luminous efficiency model. The monthly average of daily photoperiods exceeding each defined intensity (1 lx, 300 lx, … 20,000 lx) were calculated [defined as Ne(lux)]. The relationships between the monthly average of global solar radiation (Rs), N0, and Ne(lux) were investigated. At low light intensity (<500 lx), Ne(lux) were almost the same as N0. At high light intensity (>10,000 lx), Ne(lux) and Rs showed a logarithmic relationship. Using these relationships, empirical models were derived to estimate the effective day length at different light intensities. According to the validation of the model, the effective day length for any light intensity could be estimated with an accuracy of less than 11% of the mean absolute percentage error (MAPE) in the estimation of the monthly base photoperiod. Recently...

‣ Does Day Length Affect Winter Bird Distribution? Testing the Role of an Elusive Variable

Carrascal, Luis M.; Santos, Tomás; Tellería, José L.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 29/02/2012 Português
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Differences in day length may act as a critical factor in bird biology by introducing time constraints in energy acquisition during winter. Thus, differences in day length might operate as a main determinant of bird abundance along latitudinal gradients. This work examines the influence of day length on the abundance of wintering crested tits (Lophophanes cristatus) in 26 localities of Spanish juniper (Juniperus thurifera) dwarf woodlands (average height of 5 m) located along a latitudinal gradient in the Spanish highlands, while controlling for the influence of food availability, minimum night temperature, habitat structure and landscape characteristics. Top regression models in the AIC framework explained 56% of variance in bird numbers. All models incorporated day length as the variable with the highest magnitude effect. Food availability also played an important role, although only the crop of ripe juniper fruits, but not arthropods, positively affected crested tit abundance. Differences in vegetation structure across localities had also a strong positive effect (average tree height and juniper tree density). Geographical variation in night temperature had no influence on crested tit distribution, despite the low winter temperatures reached in these dwarf forests. This paper demonstrates for the first time that winter bird abundance increases with day length after controlling for the effect of other environmental variables. Winter average difference in day length was only 10.5 minutes per day along the 1°47′ latitudinal interval (190 km) included in this study. This amount of time...

‣ ZmCCT and the genetic basis of day-length adaptation underlying the postdomestication spread of maize

Hung, Hsiao-Yi; Shannon, Laura M.; Tian, Feng; Bradbury, Peter J.; Chen, Charles; Flint-Garcia, Sherry A.; McMullen, Michael D.; Ware, Doreen; Buckler, Edward S.; Doebley, John F.; Holland, James B.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Português
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Teosinte, the progenitor of maize, is restricted to tropical environments in Mexico and Central America. The pre-Columbian spread of maize from its center of origin in tropical Southern Mexico to the higher latitudes of the Americas required postdomestication selection for adaptation to longer day lengths. Flowering time of teosinte and tropical maize is delayed under long day lengths, whereas temperate maize evolved a reduced sensitivity to photoperiod. We measured flowering time of the maize nested association and diverse association mapping panels in the field under both short and long day lengths, and of a maize-teosinte mapping population under long day lengths. Flowering time in maize is a complex trait affected by many genes and the environment. Photoperiod response is one component of flowering time involving a subset of flowering time genes whose effects are strongly influenced by day length. Genome-wide association and targeted high-resolution linkage mapping identified ZmCCT, a homologue of the rice photoperiod response regulator Ghd7, as the most important gene affecting photoperiod response in maize. Under long day lengths ZmCCT alleles from diverse teosintes are consistently expressed at higher levels and confer later flowering than temperate maize alleles. Many maize inbred lines...

‣ Evolution of critical day length for diapause induction enables range expansion of Diorhabda carinulata, a biological control agent against tamarisk (Tamarix spp.)

Bean, Dan W; Dalin, Peter; Dudley, Tom L
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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In classical weed biological control, small collections of arthropods are made from one or a few sites in the native range of the target plant and are introduced to suppress the plant where it has become invasive, often across a wide geographic range. Ecological mismatches in the new range are likely, and success using the biocontrol agent may depend on postrelease evolution of beneficial life history traits. In this study, we measure the evolution of critical day length for diapause induction (day length at which 50% of the population enters dormancy), in a beetle (Diorhabda carinulata) introduced into North America from China to control an exotic shrub, Tamarix spp. Beetle populations were sampled from four sites in North America 7 years after introduction, and critical day length was shown to have declined, forming a cline over a latitudinal gradient At one field site, decreased critical day length was correlated with 16 additional days of reproductive activity, resulting in a closer match between beetle life history and the phenology of Tamarix. These findings indicate an enhanced efficacy and an increasingly wider range for D. carinulata in Tamarix control.

‣ Geographical Distribution of Adolescent Body Height with Respect to Effective Day Length in Japan: An Ecological Analysis

Yokoya, Masana; Shimizu, Hideyasu; Higuchi, Yukito
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 05/12/2012 Português
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The height of Japanese youth raised in the northern region tends to be greater than that of youth raised in the southern region; therefore, a geographical gradient in youth body height exists. Although this gradient has existed for about 100 years, the reasons for it remain unclear. Consideration of the nutritional improvement, economic growth, and intense migration that has occurred in this period indicates that it is probably the result of environmental rather than nutritional or genetic factors. To identify possible environmental factors, ecological analysis of prefecture-level data on the body size of 8- to 17-year-old youth averaged over a 13-year period (1996 to 2008) and Japanese mesh climatic data on the climatic variables of temperature, solar radiation, and effective day length (duration of photoperiod exceeding the threshold of light intensity) was performed. The geographical distribution of the standardized height of Japanese adolescents was found to be inversely correlated to a great extent with the distribution of effective day length at a light intensity greater than 4000 lx. The results of multiple regression analysis of effective day length, temperature, and weight (as an index of food intake) indicated that a combination of effective day length and weight was statistically significant as predictors of height in early adolescence; however...

‣ Responses of brain and behavior to changing day-length in the diurnal grass rat (Arvicanthis niloticus)

Leach, Greg; Ramanathan, Chidambaram; Langel, Jennifer; Yan, Lily
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Português
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Seasonal affective disorder (SAD) is a major depressive disorder that reoccurs in the fall and winter when day-lengths get short. It is well accepted that day-length is encoded by the principal circadian clock located in the suprachiasmatic nucleus (SCN), but very little is known about day-length encoding in diurnal mammals. The present study utilized the grass rat, Arvicanthis niloticus, to investigate how the circadian system responds to photoperiodic changes in a diurnal mammal that shows day-length dependent mood changes. The animals were initially housed in equatorial day-length (12hr, EP) followed by either long (16hr, LP) or short (8hr, SP) photoperiods. The LP animals showed an expansion of the peak phase of the PER1 and PER2 rhythm in the SCN as well as an extended behavioral active phase. In contrast, the SP animals did not show any compression of their active phase nor a change in the peak duration of PER1 or PER2 expression, compared to those in EP. The results suggest that the circadian system in the diurnal grass rats is less responsive when day-lengths get short compared to when they get longer. The depression-like behaviors were assessed using sweet solution preference (SSP) and forced swimming test (FST). Animals in the SP group showed decreased SSP and increased immobility time in FST as compared to the EP group...

‣ Diel Vertical Migration in Deep Sea Plankton Is Finely Tuned to Latitudinal and Seasonal Day Length

van Haren, Hans; Compton, Tanya J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 22/05/2013 Português
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46.78256%
Diel vertical migration (DVM) is a ubiquitous phenomenon in marine and freshwater plankton communities. Most commonly, plankton migrate to surface waters at dusk and return to deeper waters at dawn. Up until recently, it was thought that DVM was triggered by a relative change in visible light intensity. However, evidence has shown that DVM also occurs in the deep sea where no direct and background sunlight penetrates. To identify whether such DVM is associated with latitudinal and seasonal day light variation, one and a half years of recorded acoustic data, a measure of zooplankton abundance and movement, were examined. Acoustic Doppler current profilers, moored at eight different sub-tropical latitudes in the North-Atlantic Ocean, measured in the vertical range of 500–1600 m. DVM was observed to follow day length variation with a change in season and latitude at all depths. DVM followed the rhythm of local sunrise and sunset precisely between 500 and 650 m. It continued below 650 m, where the deepest penetrable irradiance level are <10−7 times their near-surface values, but plankton shortened their time at depth by up to about 63% at 1600 m. This suggests light was no longer a cue for DVM. This trend stayed consistent both across latitudes and between the different seasons. It is hypothesized that another mechanism...

‣ FKF1 and GIGANTEA complex formation is required for day-length measurement in Arabidopsis

Sawa, Mariko; Nusinow, Dmitri A.; Kay, Steve A.; Imaizumi, Takato
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
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Precise timing of CONSTANS (CO) gene expression is necessary for day-length discrimination for photoperiodic flowering. The FLAVIN-BINDING, KELCH REPEAT, F-BOX 1 (FKF1) and GIGANTEA (GI) proteins regulate CO transcription in Arabidopsis. We demonstrate that FKF1 and GI proteins form a complex in a blue-light dependent manner. The timing of this interaction regulates the timing of daytime CO expression. FKF1 function is dependent on GI, which interacts with a CO repressor, CYCLING DOF FACTOR 1 (CDF1), and controls CDF1 stability. GI, FKF1, and CDF1 proteins associate with CO chromatin. Thus, the FKF1-GI complex forms on the CO promoter in late afternoon to regulate CO expression, providing a mechanistic view of how the coincidence of light with circadian timing regulates photoperiodic flowering.

‣ Trade-offs between global warming and day length on the start of the carbon uptake period in seasonally cold ecosystems

Wohlfahrt, Georg; Cremonese, Edoardo; Hammerle, Albin; Hörtnagl, Lukas; Galvagno, Marta; Gianelle, Damiano; Marcolla, Barbara; di Cella, Umberto Morra
Fonte: BlackWell Publishing Ltd Publicador: BlackWell Publishing Ltd
Tipo: Artigo de Revista Científica
Português
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[1] It is well established that warming leads to longer growing seasons in seasonally cold ecosystems. Whether this goes along with an increase in the net ecosystem carbon dioxide (CO2) uptake is much more controversial. We studied the effects of warming on the start of the carbon uptake period (CUP) of three mountain grasslands situated along an elevational gradient in the Alps. To this end, we used a simple empirical model of the net ecosystem CO2 exchange, calibrated, and forced with multiyear empirical data from each site. We show that reductions in the quantity and duration of daylight associated with earlier snowmelts were responsible for diminishing returns, in terms of carbon gain, from longer growing seasons caused by reductions in daytime photosynthetic uptake and increases in nighttime losses of CO2. This effect was less pronounced at high, compared to low, elevations, where the start of the CUP occurred closer to the summer solstice when changes in day length and incident radiation are minimal.

‣ Is the target of 1 day length of stay per 1% total body surface area burned actually being achieved? A review of paediatric thermal injuries in South East Scotland

Louise, Caton Nadine; David, McGill; John, Stewart Kenneth
Fonte: e-Century Publishing Corporation Publicador: e-Century Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 22/02/2014 Português
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Objectives: Length of stay is a standard variable used to evaluate outcomes in burn care. Is the target of 1 day length of stay per 1% total body surface area burned actually being achieved? Methods: A retrospective analysis of 328 paediatric thermal injuries admitted to the South East Scotland Regional Burn Unit between January 2003 and March 2007 to assess whether the target is met and if not, which factors are contributing to a prolonged hospitalisation. Results: 57% achieved the target and 43% failed the target. Factors associated with a lengthened hospital stay were burn depth, burn location, presence of infection/sepsis and the need for theatre visits for either dressing change or surgical intervention. Conclusions: Many factors can contribute to patients’ length of hospital stay. It is valuable to identify areas of practice which can be altered to minimise the impact of these factors. For example, consider the use of laser Doppler imaging to help assess burn depth more accurately; this leading to potentially more accurate requirements for surgery or not, early excision of deep burns, improved infection control and use of dressings may all contribute to reduce the length of inpatient stay with a view to improving patient outcome.

‣ Annual Changes in Day-length, Temperature, and Circulating Reproductive Hormones in Thoroughbred Stallions and Geldings

DHAKAL, Pramod; TSUNODA, Nobuo; NAKAI, Rie; KITAURA, Tomoki; HARADA, Takehiro; ITO, Masahiro; NAGAOKA, Kentaro; TOISHI, Yuko; TANIYAMA, Hiroyuki; GEN, Watanabe; TAYA, Kazuyoshi
Fonte: The Japanese Society of Equine Science Publicador: The Japanese Society of Equine Science
Tipo: Artigo de Revista Científica
Português
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Changes in follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin, immunoreactive(ir)-inhibin, testosterone, estradiol-17β, and insulin-like growth factor (IGF)-I in Thoroughbred stallions along with changes in prolactin secretion in geldings were studied. The correlations of day-length with changes in the concentrations of these hormones were also studied. Five stallions and thirteen geldings were employed to draw blood samples in monthly basis and radioimmunoassay was performed to measure these hormones. All hormones showed a seasonal pattern, the levels being highest during the breeding season and lowest during the winter months. Most of the hormones were at their highest concentration during the month of April, the mid of spring in northern hemisphere. The concentration of circulating IGF-I also demonstrated seasonality, the peak lying on the month of April. The plasma concentration of prolactin also increased during the breeding season. This phenomenon was similar both in stallions and geldings although geldings had lower concentration than that of stallions. The changes in concentration of prolactin in stallions and geldings correlated more towards the day-length than towards the temperature. These results clearly indicate the seasonality of pituitary and gonadal hormones of Thoroughbred stallions...

‣ Day-length is central to maintaining consistent seasonal diversity in marine bacterioplankton

Jack A. Gilbert; Paul Somerfield; Ben Temperton; Susan Huse; Ian Joint; Dawn Field
Fonte: Nature Preceedings Publicador: Nature Preceedings
Tipo: Manuscript
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Marine bacterial diversity is vast, but seasonal variation in diversity is poorly understood. Here we present the longest bacterial diversity time series consisting of monthly (72) samples from the western English Channel over a 6 year period (2003-2008) using 747,494 16SrDNA-V6 amplicon-pyrosequences. Although there were characteristic cycles for each phylum, the overall community cycle was remarkably stable year after year. The majority of taxa were not abundant, although on occasion these rare bacteria could dominate the assemblage. Bacterial diversity peaked at the winter solstice and showed remarkable synchronicity with day-length, which had the best explanatory power compared to a combination of other variables (including temperature and nutrient concentrations). Day-length has not previously been recognised as a major force in structuring microbial communities.

‣ Chia flowering season prediction using day length data of 11 selected locations

Ayerza (h.),Ricardo
Fonte: Revista industrial y agrícola de Tucumán Publicador: Revista industrial y agrícola de Tucumán
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2014 Português
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Chia (Salvia hispanica L.) is an annual herb of the Lamiaceae family. In pre-Columbian times, its seeds were one of the basic foods of Central American civilizations. Recently, chia seed has been given an important role in human health and nutrition, because its w-3 fatty acid content promotes beneficial health effects. Efforts to incorporate chia into modern agriculture only began in 1990. However, a number of chia plantations have failed lately in Northwestern Argentina, Southeast Bolivia and South Paraguay, because the fact that chia shows a short-day response to flowering and is not a frost-resistant plant has been overlooked. This technical note aims to determine the photoperiod needed for chia flowering, apart from predicting its flowering season when there are not any chia production records. The results collectively indicate a relatively narrow set of conditions for optimal chia flowering, with optimal flowering considered to be the case of fast-developing plants with many flower buds and a satisfactory height. Chia plants were only able to flower when day length was shorter than 12:27 hours. This suggests a critical day length that ranges between 12 and 13 hours.