The Mechanism of Rhythmic Ethylene Production in Sorghum. The Role of Phytochrome B and Simulated Shading1

Mutant sorghum (Sorghum bicolor [L.] Moench) deficient in functional phytochrome B exhibits reduced photoperiodic sensitivity and constitutively expresses a shade-avoidance phenotype. Under relatively bright, high red:far-red light, ethylene production by seedlings of wild-type and phytochrome B-mutant cultivars progresses through cycles in a circadian rhythm; however, the phytochrome B mutant produces ethylene peaks with approximately 10 times the amplitude of the wild type. Time-course northern blots show that the mutant's abundance of the 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase mRNA SbACO2 is cyclic and is commensurate with ethylene production, and that ACC oxidase activity follows the same pattern. Both SbACO2 abundance and ACC oxidase activity in the wild-type plant are very low under this regimen. ACC levels in the two cultivars did not demonstrate fluctuations coincident with the ethylene produced. Simulated shading caused the wild-type plant to mimic the phenotype of the mutant and to produce high amplitude rhythms of ethylene evolution. The circadian feature of the ethylene cycle is conditionally present in the mutant and absent in the wild-type plant under simulated shading. SbACO2 abundance in both cultivars demonstrates a high-amplitude diurnal cycle under these conditions; however, ACC oxidase activity, although elevated, does not exhibit a clear rhythm correlated with ethylene production. ACC levels in both cultivars show fluctuations corresponding to the ethylene rhythm previously observed. It appears that at least two separate mechanisms may be involved in generating high-amplitude ethylene rhythms in sorghum, one in response to the loss of phytochrome B function and another in response to shading.

Photosystem II Cyclic Heterogeneity and Photoactivation in the Diazotrophic, Unicellular Cyanobacterium Cyanothece Species ATCC 511421

The unicellular, diazotrophic cyanobacterium Cyanothece sp. ATCC 51142 demonstrated important modifications to photosystem II (PSII) centers when grown under light/dark N2-fixing conditions. The properties of PSII were studied throughout the diurnal cycle using O2-flash-yield and pulse-amplitude-modulated fluorescence techniques. Nonphotochemical quenching (qN) of PSII increased during N2 fixation and persisted after treatments known to induce transitions to state 1. The qN was high in cells grown in the dark, and then disappeared progressively during the first 4 h of light growth. The photoactivation probability, ε, demonstrated interesting oscillations, with peaks near 3 h of darkness and 4 and 10 h of light. Experiments and calculations of the S-state distribution indicated that PSII displays a high level of heterogeneity, especially as the cells prepare for N2 fixation. We conclude that the oxidizing side of PSII is strongly affected during the period before and after the peak of nitrogenase activity; changes include a lowered capacity for O2 evolution, altered dark stability of PSII centers, and substantial changes in qN.

The importance of the diurnal and annual cycle of air traffic for contrail radiative forcing

Air traffic condensation trails, or contrails, are believed to have a net atmospheric warming effect(1), although one that is currently small compared to that induced by other sources of human emissions. However, the comparably large growth rate of air traffic requires an improved understanding of the resulting impact of aircraft radiative forcing on climate(2). Contrails have an effect on the Earth's energy balance similar to that of high thin ice clouds(3). Their trapping of outgoing longwave radiation emitted by the Earth and atmosphere (positive radiative forcing) is partly compensated by their reflection of incoming solar radiation (negative radiative forcing). On average, the longwave effect dominates and the net contrail radiative forcing is believed to be positive(1,2,4). Over daily and annual timescales, varying levels of air traffic, meteorological conditions, and solar insolation influence the net forcing effect of contrails. Here we determine the factors most important for contrail climate forcing using a sophisticated radiative transfer model(5,6) for a site in southeast England, located in the entrance to the North Atlantic flight corridor. We find that night-time flights during winter (December to February) are responsible for most of the contrail radiative forcing. Night flights account for only 25 per cent of daily air traffic, but contribute 60 to 80 per cent of the contrail forcing. Further, winter flights account for only 22 per cent of annual air traffic, but contribute half of the annual mean forcing. These results suggest that flight rescheduling could help to minimize the climate impact of aviation.

Turbulence in Small Sub-Tropical Estuary with Semi-Diurnal Tides

In natural estuaries, contaminant transport is driven by the turbulent momentum mixing. The predictions of scalar dispersion can rarely be predicted accurately because of a lack of fundamental understanding of the turbulence structure in estuaries. Herein detailed turbulence field measurements were conducted at high frequency and continuously for up to 50 hours per investigation in a small subtropical estuary with semi-diurnal tides. Acoustic Doppler velocimetry was deemed the most appropriate measurement technique for such small estuarine systems with shallow water depths (less than 0.5 m at low tides), and a thorough post-processing technique was applied. The estuarine flow is always a fluctuating process. The bulk flow parameters fluctuated with periods comparable to tidal cycles and other large-scale processes. But turbulence properties depended upon the instantaneous local flow properties. They were little affected by the flow history, but their structure and temporal variability were influenced by a variety of mechanisms. This resulted in behaviour which deviated from that for equilibrium turbulent boundary layer induced by velocity shear only. A striking feature of the data sets is the large fluctuations in all turbulence characteristics during the tidal cycle. This feature was rarely documented, but an important difference between the data sets used in this study from earlier reported measurements is that the present data were collected continuously at high frequency during relatively long periods. The findings bring new lights in the fluctuating nature of momentum exchange coefficients and integral time and length scales. These turbulent properties should not be assumed constant.

Diurnal inhibition of NMDA-EPSCs at rat hippocampal mossy fibre synapses through orexin-2 receptors.

Diurnal release of the orexin neuropeptides orexin-A (Ox-A, hypocretin-1) and orexin-B (Ox-B, hypocretin-2) stabilises arousal, regulates energy homeostasis and contributes to cognition and learning. However, whether cellular correlates of brain plasticity are regulated through orexins, and whether they do so in a time-of-day-dependent manner, has never been assessed. Immunohistochemically we found sparse but widespread innervation of hippocampal subfields through Ox-A- and Ox-B-containing fibres in young adult rats. The actions of Ox-A were studied on NMDA receptor (NMDAR)-mediated excitatory synaptic transmission in acute hippocampal slices prepared around the trough (Zeitgeber time (ZT) 4-8, corresponding to 4-8 h into the resting phase) and peak (ZT 23) of intracerebroventricular orexin levels. At ZT 4-8, exogenous Ox-A (100 nm in bath) inhibited NMDA receptor-mediated excitatory postsynaptic currents (NMDA-EPSCs) at mossy fibre (MF)-CA3 (to 55.6 ± 6.8% of control, P = 0.0003) and at Schaffer collateral-CA1 synapses (70.8 ± 6.3%, P = 0.013), whereas it remained ineffective at non-MF excitatory synapses in CA3. Ox-A actions were mediated postsynaptically and blocked by the orexin-2 receptor (OX2R) antagonist JNJ10397049 (1 μm), but not by orexin-1 receptor inhibition (SB334867, 1 μm) or by adrenergic and cholinergic antagonists. At ZT 23, inhibitory effects of exogenous Ox-A were absent (97.6 ± 2.9%, P = 0.42), but reinstated (87.2 ± 3.3%, P = 0.002) when endogenous orexin signalling was attenuated for 5 h through i.p. injections of almorexant (100 mg kg(-1)), a dual orexin receptor antagonist. In conclusion, endogenous orexins modulate hippocampal NMDAR function in a time-of-day-dependent manner, suggesting that they may influence cellular plasticity and consequent variations in memory performance across the sleep-wake cycle.

Genome-wide RNA polymerase II profiles and RNA accumulation reveal kinetics of transcription and associated epigenetic changes during diurnal cycles.

Interactions of cell-autonomous circadian oscillators with diurnal cycles govern the temporal compartmentalization of cell physiology in mammals. To understand the transcriptional and epigenetic basis of diurnal rhythms in mouse liver genome-wide, we generated temporal DNA occupancy profiles by RNA polymerase II (Pol II) as well as profiles of the histone modifications H3K4me3 and H3K36me3. We used these data to quantify the relationships of phases and amplitudes between different marks. We found that rhythmic Pol II recruitment at promoters rather than rhythmic transition from paused to productive elongation underlies diurnal gene transcription, a conclusion further supported by modeling. Moreover, Pol II occupancy preceded mRNA accumulation by 3 hours, consistent with mRNA half-lives. Both methylation marks showed that the epigenetic landscape is highly dynamic and globally remodeled during the 24-hour cycle. While promoters of transcribed genes had tri-methylated H3K4 even at their trough activity times, tri-methylation levels reached their peak, on average, 1 hour after Pol II. Meanwhile, rhythms in tri-methylation of H3K36 lagged transcription by 3 hours. Finally, modeling profiles of Pol II occupancy and mRNA accumulation identified three classes of genes: one showing rhythmicity both in transcriptional and mRNA accumulation, a second class with rhythmic transcription but flat mRNA levels, and a third with constant transcription but rhythmic mRNAs. The latter class emphasizes widespread temporally gated posttranscriptional regulation in the mouse liver.

Effect of diurnal cycling temperatures on cardiovascular- ventilatory function in statically-acclimated rainbow trout, Salmo gairdneri

Four groups of rainbow trout, Salmo gairdneri, were acclimated to 2°, 10°, and 18°e, and to a diurnal temperature cycle (100 ± 4°C). To evaluate the influence of cycling temperatures in terms of an immediate as opposed to acclimatory response various ventilatory-cardiovascular rate functions were observed for trout, either acclimated to cycling temperatures or acclimated to constant temperatures and exposed to a diurnal temperature cycle for the first time (10° ± 4°C for trout acclimated to 10°C; 18°+ 4°C for trout acclimated to l8°e). Gill resistance and the cardiac to ventilatory rate ratio were then calculated. Following a post preparatory recovery period of 36 hr, measurements were made over a 48 hour period with the first 24 hours being at constant temperature in the case of statically-acclimated fish followed by 24 hours under cyclic temperature conditions. Trout exhibited marked changes in oxygen consumption (Vo ) with temp- 2 erature both between acclimation groups, and in response to the diurnal temperature cycle. This increase in oxygen uptake appears to have been achieved by adjustment of ventilatory and, to some extent, cardiovascular activity. Trout exhibited significant changes in ventilatory rate (VR), stroke volume (Vsv), and flow (VG) in response to temperature. Marked changes in cardiac rate were also observed. These findings are discussed in relation to their importance in convective oxygen transport via water and blood at the gills and tissues. Trout also exhibited marked changes in pressure waveforms associated with the action of the resp; ratory pumps with temperature. Mean differenti a 1 pressure increased with temperature as did gill resistance and utilization. This data is discussed in relation to its importance in diffusive oxygen transport and the conditions for gas exchange at the gills. With one exception, rainbow trout were able to respond to changes in oxygen demand and availability associated with changes in temperature by means of adjustments in ventilation, and possibly pafusion, and the conditions for gas exchange at the gills. Trout acclimated to 18°C, however, and exposed to high cyclic temperatures, showed signs of the ventilatory and cardiovascular distress problems commonly associated with low circulating levels of oxygen in the blood. It appears these trout were unable to fully meet the oxygen requirements associated with c~ling temperatures above 18°C. These findings were discussed in relation to possible limitations in the cardiovascular-ventilatory response at high temperatures. The response of trout acclimated to cycling temperatures was generally similar to that for trout acclimated to constant temperatures and exposed to cycling temperatures for the first time. This result suggested that both groups of fish may have been acclimated to a similar thermal range, regardless of the acclimation regime employed. Such a phenomenon would allow trout of either acclimation group to respond equally well to the imposed temperature cycle. Rainbow trout showed no evidence of significant diurnal rhythm in any parameters observed at constant temperatures (2°, 10°, and 18° C), and under a 12/12 light-dark photoperiod regime. This was not taken to indicate an absence of circadian rhythms in these trout, but rather a deficiency in the recording methods used in the study.

The impact of diurnal variability in sea surface temperature on the atlantic air-sea CO2 flux

The effect of diurnal variations in sea surface temperature (SST) on the air-sea flux of CO2 over the central Atlantic ocean and Mediterranean Sea (60 S–60 N, 60 W–45 E) is evaluated for 2005–2006. We use high spatial resolution hourly satellite ocean skin temperature data to determine the diurnal warming (ΔSST). The CO2 flux is then computed using three different temperature fields – a foundation temperature (Tf, measured at a depth where there is no diurnal variation), Tf, plus the hourly ΔSST and Tf, plus the monthly average of the ΔSSTs. This is done in conjunction with a physically-based parameterisation for the gas transfer velocity (NOAA-COARE). The differences between the fluxes evaluated for these three different temperature fields quantify the effects of both diurnal warming and diurnal covariations. We find that including diurnal warming increases the CO2 flux out of this region of the Atlantic for 2005–2006 from 9.6 Tg C a−1 to 30.4 Tg C a−1 (hourly ΔSST) and 31.2 Tg C a−1 (monthly average of ΔSST measurements). Diurnal warming in this region, therefore, has a large impact on the annual net CO2 flux but diurnal covariations are negligible. However, in this region of the Atlantic the uptake and outgassing of CO2 is approximately balanced over the annual cycle, so although we find diurnal warming has a very large effect here, the Atlantic as a whole is a very strong carbon sink (e.g. −920 Tg C a−1 Takahashi et al., 2002) making this is a small contribution to the Atlantic carbon budget.

Observations of diurnal and spatial variability of radiative forcing by equatorial deep convective clouds

From geostationary satellite observations of equatorial Africa and the equatorial east Atlantic during May and June 2000 we explore the radiative forcing by deep convective cloud systems in these regions. Deep convective clouds (DCCs) are associated with a mean radiative forcing relative to non–deep convective areas of −39 W m−2 over the Atlantic Ocean and of +13 W m−2 over equatorial Africa (±10 W m−2 in both cases). We show that over land the timing of the daily cycle of convection relative to the daily cycle in solar illumination and surface temperature significantly affects the mean radiative forcing by DCCs. Displacement of the daily cycle of DCC coverage by 2 hours changes their overall radiative effect by ∼10 W m−2, with implications for the simulation of the radiative balance in this region. The timing of the minimum DCC cover over land, close to noon local time, means that the mean radiative forcing is nearly maximized.

Reconstruction of geomagnetic activity and near-Earth interplanetary conditions over the past 167 yr - Part 3: improved representation of solar cycle 11

Svalgaard (2014) has recently pointed out that the calibration of the Helsinki magnetic observatory’s H component variometer was probably in error in published data for the years 1866–1874.5 and that this makes the interdiurnal variation index based on daily means, IDV(1d), (Lockwood et al., 2013a), and the interplanetary magnetic field strength derived from it (Lockwood et al., 2013b), too low around the peak of solar cycle 11. We use data from the modern Nurmijarvi station, relatively close to the site of the original Helsinki Observatory, to confirm a 30% underestimation in this interval and hence our results are fully consistent with the correction derived by Svalgaard. We show that the best method for recalibration uses the Helsinki Ak(H) and aa indices and is accurate to ±10 %. This makes it preferable to recalibration using either the sunspot number or the diurnal range of geomagnetic activity which we find to be accurate to ±20 %. In the case of Helsinki data during cycle 11, the two recalibration methods produce very similar corrections which are here confirmed using newly digitised data from the nearby St Petersburg observatory and also using declination data from Helsinki. However, we show that the IDV index is, compared to later years, too similar to sunspot number before 1872, revealing independence of the two data series has been lost; either because the geomagnetic data used to compile IDV has been corrected using sunspot numbers, or vice versa, or both. We present corrected data sequences for both the IDV(1d) index and the reconstructed IMF (interplanetary magnetic field).We also analyse the relationship between the derived near-Earth IMF and the sunspot number and point out the relevance of the prior history of solar activity, in addition to the contemporaneous value, to estimating any “floor” value of the near-Earth interplanetary field.

Circadian variation with a diurnal bimodal profile on scent-marking behavior in captive common marmosets (callitrhix jacchus)

Scent-marking behavior is associated with different behavioral contexts in callitrichids, including signalizing a territory, location of feeding resources, and social rank. In marmosets and tamarins it is also associated with intersexual communication. Though it appears very important for the daily routine of the individuals, very few researchers have investigated distribution through the 24-h cycle. In a preliminary report, we described a preferential incidence of this behavior 2 h before nocturnal rest in families of common marmosets. We expand the data using 8 family groups (28 subjects), 8 fathers, 6 mothers, 8 nonreproductive adults (4 sons and 4 daughters), and 6 juvenile (3 sons and 3 daughters) offspring that we kept in outdoor cages under natural environmental conditions. We recorded the frequency of anogenital scent marking for each group during the light phase, twice a wk, for 4 consecutive wks, from March 1998 to September 1999. Cosinor test detected 24- and 8-h variations in 89.3% and 85.7% of the subjects, respectively, regardless of sex or reproductive status. The 8-h component is a consequence of the 2 peaks for the behavior, at the beginning and end of the light phase. Daily distribution of scent marking is similar to that others described previously for motor activity in marmosets. The coincident rhythmical patterns for both behaviors seem to be associated with feeding behavior, as described for callitrichids in free-ranging conditions, involving an increase in foraging activities early in the morning and shortly before nocturnal rest

Adrenergic response patterns in vas deferens isolated from rats under diurnal rhythms - Influence of stress

The aim of this study was to verify, by means of functional methods, whether the circadian rhythm changes adrenergic response patterns in the epididymal half of the vas deferens isolated from control rats as well as from rats submitted to acute stress. The experiments were performed at 9:00 a.m., 3:00 p.m., 9:00 p.m., and 3:00 a.m. The results showed a light-dark dependent variation of the adrenergic response pattern on organs isolated from control as well as from stressed rats. In the control group, only the phenylephrine sensitivity was changed throughout the circadian rhythm. Under the stress condition, both norepinephrine and phenylephrine response patterns were changed, mainly during darkness. The maximal contractile response to both alpha- and beta-agonist and alpha(1)-agonist was increased in the dark phase, corresponding to high plasmatic concentrations of endogenous melatonin. The vas deferens isolated from stressed rats during the light phase simultaneously incubated with exogenous melatonin showed the same pattern of response obtained in the dark phase, thus indicating a peripheric action of melatonin on this organ. Therefore, the circadian rhythms are important to the adrenergic response pattern in rat vas deferens from both control and stressed rats. In conclusion, we suggest a melatonin modulation on alpha(1)-postsynaptic adrenergic response in the rat vas deferens. (c) 2005 Elsevier B.V. All rights reserved.

Daily ozone cycle in the stratosphere: global, regional and seasonal behaviour modelled with the Whole Atmosphere Community Climate Model

The Whole Atmosphere Community Climate Model (WACCM) is utilised to study the daily ozone cycle and underlying photochemical and dynamical processes. The analysis is focused on the daily ozone cycle in the middle stratosphere at 5 hPa where satellite-based trend estimates of stratospheric ozone are most biased by diurnal sampling effects and drifting satellite orbits. The simulated ozone cycle shows a minimum after sunrise and a maximum in the late afternoon. Further, a seasonal variation of the daily ozone cycle in the stratosphere was found. Depending on season and latitude, the peak-to-valley difference of the daily ozone cycle varies mostly between 3 and 5% (0.4 ppmv) with respect to the midnight ozone volume mixing ratio. The maximal variation of 15% (0.8 ppmv) is found at the polar circle in summer. The global pattern of the strength of the daily ozone cycle is mainly governed by the solar zenith angle and the sunshine duration. In addition, we find synoptic-scale variations in the strength of the daily ozone cycle. These variations are often anti-correlated to regional temperature anomalies and are due to the temperature dependence of the rate coefficients k2 and k3 of the Chapman cycle reactions. Further, the NOx catalytic cycle counteracts the accumulation of ozone during daytime and leads to an anti-correlation between anomalies in NOx and the strength of the daily ozone cycle. Similarly, ozone recombines with atomic oxygen which leads to an anti-correlation between anomalies in ozone abundance and the strength of the daily ozone cycle. At higher latitudes, an increase of the westerly (easterly) wind cause a decrease (increase) in the sunshine duration of an air parcel leading to a weaker (stronger) daily ozone cycle.

Circadian variation with a diurnal bimodal profile on scent-marking behavior in captive common marmosets (callitrhix jacchus)

Scent-marking behavior is associated with different behavioral contexts in callitrichids, including signalizing a territory, location of feeding resources, and social rank. In marmosets and tamarins it is also associated with intersexual communication. Though it appears very important for the daily routine of the individuals, very few researchers have investigated distribution through the 24-h cycle. In a preliminary report, we described a preferential incidence of this behavior 2 h before nocturnal rest in families of common marmosets. We expand the data using 8 family groups (28 subjects), 8 fathers, 6 mothers, 8 nonreproductive adults (4 sons and 4 daughters), and 6 juvenile (3 sons and 3 daughters) offspring that we kept in outdoor cages under natural environmental conditions. We recorded the frequency of anogenital scent marking for each group during the light phase, twice a wk, for 4 consecutive wks, from March 1998 to September 1999. Cosinor test detected 24- and 8-h variations in 89.3% and 85.7% of the subjects, respectively, regardless of sex or reproductive status. The 8-h component is a consequence of the 2 peaks for the behavior, at the beginning and end of the light phase. Daily distribution of scent marking is similar to that others described previously for motor activity in marmosets. The coincident rhythmical patterns for both behaviors seem to be associated with feeding behavior, as described for callitrichids in free-ranging conditions, involving an increase in foraging activities early in the morning and shortly before nocturnal rest

Circadian variation with a diurnal bimodal profile on scent-marking behavior in captive common marmosets (callitrhix jacchus)

Scent-marking behavior is associated with different behavioral contexts in callitrichids, including signalizing a territory, location of feeding resources, and social rank. In marmosets and tamarins it is also associated with intersexual communication. Though it appears very important for the daily routine of the individuals, very few researchers have investigated distribution through the 24-h cycle. In a preliminary report, we described a preferential incidence of this behavior 2 h before nocturnal rest in families of common marmosets. We expand the data using 8 family groups (28 subjects), 8 fathers, 6 mothers, 8 nonreproductive adults (4 sons and 4 daughters), and 6 juvenile (3 sons and 3 daughters) offspring that we kept in outdoor cages under natural environmental conditions. We recorded the frequency of anogenital scent marking for each group during the light phase, twice a wk, for 4 consecutive wks, from March 1998 to September 1999. Cosinor test detected 24- and 8-h variations in 89.3% and 85.7% of the subjects, respectively, regardless of sex or reproductive status. The 8-h component is a consequence of the 2 peaks for the behavior, at the beginning and end of the light phase. Daily distribution of scent marking is similar to that others described previously for motor activity in marmosets. The coincident rhythmical patterns for both behaviors seem to be associated with feeding behavior, as described for callitrichids in free-ranging conditions, involving an increase in foraging activities early in the morning and shortly before nocturnal rest