Constant Low Temperature Research Articles

The effects of cold stress on the phenolic compounds and antioxidant capacity of grapevine (Vitis vinifera L.) leaves

According to some estimates, a 70% increase in crop yield could be achieved if the environmental conditions were close to the optimum ones for a given plant, which is why the identification and control of adverse environmental effects is a top priority in many countries worldwide. This paper contains a discussion of the changes in selected elements of the secondary metabolism in the leaves of two grapevine varieties (Vitis vinifera L.) with a different degree of tolerance to cold stress during prolonged and constant low temperature stress. The analyses have shown that the more-tolerant variety was characterized by a higher content of phenolic compounds, better radical-scavenging capacity and stronger reducing power. However, the cold stress caused a decrease in the concentration of the phenolics and decreased the scavenging capacity in the leaves of both varieties. Four phenolic acids have been identified in the extracts from the leaves of both grapevines: caffeic acid, p-coumaric acid, ferulic acid and a caffeic acid derivative. Caffeic acid appeared in the highest concentrations in all the leaf extracts. Additionally, it has been noted that in the leaves of the varieties susceptible and tolerant to cold stress, the prolonged exposure to low temperature caused a considerable reduction of the content of all identified phenolic acids. The results of the analyses have demonstrated large differences in the functioning of the secondary metabolism in response to the same stressor.

Fish Energy Use among Fluctuating and Constant Thermal Regimes Simulating Winter Conditions in Rivers

AbstractDuring the winter, variation in water temperature in temperate‐zone rivers is strongly influenced by the presence or absence of surface ice cover. Prior to ice formation, water temperatures can fluctuate from nighttime lows near 0°C to daytime highs near 6°C. After ice formation, temperatures remain constant near 0°C. Climate change is projected to reduce the duration of surface ice cover in aquatic ecosystems and, thus, alter winter temperature regimes. We conducted a laboratory experiment to compare fish energy use for two situations: (1) ice free conditions with diel cycling temperatures (0.2–6°C), and (2) ice cover conditions with constant low temperatures (0.5°C). We compared the response of Creek Chub Semotilus atromaculatus, representing a coolwater species, and Brook Trout Salvelinus fontinalis, representing a coldwater species, to these temperature regimes. During a 60‐d study we monitored metabolic measurements of energy use and proximate body composition of fasted fish. For Creek Chub, there was no effect of time or temperature regime on respiration rates. Ammonium excretion declined over time for Creek Chub held at the constant low temperature but remained unchanged for fish held at the cycling temperature. For Brook Trout, there was no effect of time or temperature regime on respiration or ammonium excretion. Both species showed a loss of body lipids over the 60 d but there was no difference in the rate of loss between the two temperature treatments. Thus, we were unable to detect a difference in the energy use for these species between the different thermal regimes simulating the presence or absence of surface ice cover.

Effect of cold storage on the biological fitness of Encarsia sophia (Hymenoptera: Aphelinidae), a parasitoid of Bemisia tabaci (Hemiptera: Aleyrodidae)

Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) is an important bio-control agent of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae). Storage at low temperature is a valuable method used in the mass rearing of biological control agents to ensure the availability of sufficient parasitoids when needed. However, storing parasitoids at a low temperature may lead to a decrease in their fitness. The aim of this study was to determine the effect of different durations of constant low temperature storage on the fitness traits of the above parasitoid. The effect of storage at three temperatures (4, 8 and 12 ± 1°C, RH = 65-75% and in darkness) for periods of 1, 2 or 3 weeks and at two pupal stages (10 and 12 days old) was studied. The percentage emergence, time to emergence, longevity, size and ability of the females that emerged to parasitize B. tabaci were evaluated. The results indicate that there is a decrease in percentage emergence, longevity and ability to parasitize the longer and lower the temperature at which the pupae of E. sophia are stored. The percentage emergence of both pupal stages kept at 12°C for a week was not affected. However, at lower temperatures (8 and 4°C) percentage emergence after storage of two weeks decreased to 67-87.5% and after three weeks none emerged. The time to adult emergence was longer for 12 day old pupae at all temperatures and storage times. The longevity of the adults that emerged from both pupal stages after one week of storage at 12 and 8°C was not affected, but decreased to 66-72% with increase in storage time. There was no effect of cold storage on adult size when 10 day old pupae were stored. The ability of this parasitoid to parasitize B. tabaci after emerging from both pupal stages stored at all of the temperatures regardless of storage time was significantly lower. Effect of storage at 12°C for a week in terms of percentage emergence and longevity did not differ from that of the control, but nevertheless they were less able to parasitize B. tabaci. Although the information on the effect of cold storage on E. sophia is very limited, the results of this study indicate that for more efficient biological control there is an urgent need to improve the method of storing pupae.

Morphological divergence between three Arctic charr morphs - the significance of the deep-water environment.

Morphological divergence was evident among three sympatric morphs of Arctic charr (Salvelinus alpinus (L.)) that are ecologically diverged along the shallow-, deep-water resource axis in a subarctic postglacial lake (Norway). The two deep-water (profundal) spawning morphs, a benthivore (PB-morph) and a piscivore (PP-morph), have evolved under identical abiotic conditions with constant low light and temperature levels in their deep-water habitat, and were morphologically most similar. However, they differed in important head traits (e.g., eye and mouth size) related to their different diet specializations. The small-sized PB-morph had a paedomorphic appearance with a blunt head shape, large eyes, and a deep body shape adapted to their profundal lifestyle feeding on submerged benthos from soft, deep-water sediments. The PP-morph had a robust head, large mouth with numerous teeth, and an elongated body shape strongly related to their piscivorous behavior. The littoral spawning omnivore morph (LO-morph) predominantly utilizes the shallow benthic–pelagic habitat and food resources. Compared to the deep-water morphs, the LO-morph had smaller head relative to body size. The LO-morph exhibited traits typical for both shallow-water benthic feeding (e.g., large body depths and small eyes) and planktivorous feeding in the pelagic habitat (e.g., streamlined body shape and small mouth). The development of morphological differences within the same deep-water habitat for the PB- and PP-morphs highlights the potential of biotic factors and ecological interactions to promote further divergence in the evolution of polymorphism in a tentative incipient speciation process. The diversity of deep-water charr in this study represents a novelty in the Arctic charr polymorphism as a truly deep-water piscivore morph has to our knowledge not been described elsewhere.

Microarray transcriptional profiling of Arctic Mesorhizobium strain N33 at low temperature provides insights into cold adaption strategies.

BackgroundArctic Mesorhizobium strain N33 was isolated from nodules of the legume Oxytropis arctobia in Canada’s eastern Arctic. This symbiotic bacterium can grow at temperatures ranging from 0 to 30 °C, fix nitrogen at 10 °C, and is one of the best known cold-adapted rhizobia. Despite the economic potential of this bacterium for northern regions, the key molecular mechanisms of its cold adaptation remain poorly understood.ResultsUsing a microarray printed with 5760 Arctic Mesorhizobium genomic clones, we performed a partial transcriptome analysis of strain N33 grown under eight different temperature conditions, including both sustained and transient cold treatments, compared with cells grown at room temperature. Cells treated under constant (4 and 10 °C) low temperatures expressed a prominent number of induced genes distinct from cells treated to short-term cold-exposure (<60 min), but exhibited an intermediate expression profile when exposed to a prolonged cold exposure (240 min). The most prominent up-regulated genes encode proteins involved in metabolite transport, transcription regulation, protein turnover, oxidoreductase activity, cryoprotection (mannitol, polyamines), fatty acid metabolism, and membrane fluidity. The main categories of genes affected in N33 during cold treatment are sugar transport and protein translocation, lipid biosynthesis, and NADH oxidoreductase (quinone) activity. Some genes were significantly down-regulated and classified in secretion, energy production and conversion, amino acid transport, cell motility, cell envelope and outer membrane biogenesis functions. This might suggest growth cessation or reduction, which is an important strategy to adjust cellular function and save energy under cold stress conditions.ConclusionOur analysis revealed a complex series of changes associated with cold exposure adaptation and constant growth at low temperatures. Moreover, it highlighted some of the strategies and different physiological states that Mesorhizobium strain N33 has developed to adapt to the cold environment of the Canadian high Arctic and has revealed candidate genes potentially involved in cold adaptation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1611-4) contains supplementary material, which is available to authorized users.

Modelling of the mixed convection in a lid-driven cavity with a constant heat flux boundary condition

In this paper steady state two-dimensional mixed convection heat transfer problem in a lid-driven cavity heated via an uniformly distributed heat flux on the bottom wall is investigated numerically. The lid moves with constant velocity and is kept at low constant temperature, between two ideally thermally insulated vertical walls. A wide range of Prandtl Pr and Richardson Ri number is examined to study their effects on heat transfer rate and fluid flow. Governing parameters are 0.001 ≤ Ri ≤ 1.0 and 0.71 ≤ Pr ≤ 56.00. Grashof number Gr is fixed at 104. The results are presented in the form of isotherms and streamlines plots. Also, local and mean Nusselt number are depicted on charts. Numerical values of the surface averaged Nusselt number are also presented. Results show that increase of Prandtl number strongly influences enhancement of heat transfer rate and that decreasing of Richardson number increases surface averaged Nusselt number. Mechanisms responsible for intensification of heat transfer are identified and physical explanation of this phenomenon are also given.

Numerical study of natural convection heat transfer from a heater placed in an enclosure with adjacent inclined sidewall

In this investigation , natural convection heat transfer from a heater placed on the bottom of a square enclosure with adjacent inclined wall was carried out . The inclined wall has a constant lowtemperature , while the heater element has a constant high temperature ,and the remaining walls are insulated . The working fluid used is air with Prandtl number (Pr=0.72) . The governing equations of the problem are solved numerically by using finite differencemethod . The numerical solution is presented for various Rayligh numbers,Ra(103-105) , with different dimensionless parameters as length of heater (Yh¬) (0.1,0.3,0.5), different locations of the heater (Xh) (0.25,0.5) and inclination angle of inclined cold wall  (10o, 20o, 30o). The results are presented by isotherms and streamlines to show the behavior of the flow and temperature distribution .While the numerical results of heat transfer are presented by average Nusselt number and local Nusselt numbers at right , left and top sides of heater.The results show the effect of dimensionless parameters on heat transfer and Nusselt number.It is observed that the Nusselt number increased by increasing Raylig number , heater length , inclination angle of cold wall and where the heater is near the cold wall (Xh=0.5).

Free convection heat transfer and fluid flow of Cu–water nanofluids inside a triangular–cylindrical annulus

In this paper, natural convection flow and heat transfer of Cu–water nanofluids in a horizontal triangular–cylindrical annulus is investigated numerically. The inner circular cylinder is maintained at a constant high temperature of TH whereas the outer triangular cylinder is kept at a constant low temperature of Tc. The governing equations are derived in the form of stream function-vorticity formulation and solved using control volume based finite element method (CVFEM). Theoretical models of Maxwell–Garnetts (MG) and Brinkman are employed to predict the thermal conductivity and viscosity of the nanofluid respectively. The effects of Rayleigh number, nanoparticles and annulus radius ratio on fluid flow and temperature field are plotted and discussed. The results indicate that the average Nusselt number increases with increasing the radius ratio at higher Rayleigh numbers, whereas it decreases at lower Rayleigh numbers. It also reveals that heat transfer is augmented by adding the nanoparticles to the base fluid. Moreover percentage of heat transfer enhancement caused by the nanofluid is more remarkable at lower Rayleigh numbers.

Mixed-convection flow and heat transfer in an inclined cavity equipped to a hot obstacle using nanofluids considering temperature-dependent properties

Mixed-convection fluid flow and heat transfer in a square cavity filled with Al2O3–water nanofluid have been numerically investigated using the finite volume method (FVM) and SIMPLER algorithm. The geometry is a lid-driven square enclosure with an interior rectangular heated obstacle. The bottom, top, and left walls are adiabatic while the right wall has a constant low temperature (Tc). The upper lid of the cavity moves in a positive direction. Effects of different key parameters such as Richardson number, position and height of the block, the volume fraction of the nanoparticles, and cavity inclination angles on the fluid flow and heat transfer inside the cavity are investigated. It is observed that the average Nusselt number for all ranges of solid volume fraction increases with a decrease in the Richardson number. The results elucidate irregular changes of mean Nusselt number at different Richardson numbers versus variation of inclination angles in any case.

Influence of temperature during grain filling on gluten viscoelastic properties and gluten protein composition.

The aim of this study was to investigate the effects of low to moderate temperatures on gluten functionality and gluten protein composition. Four spring wheat cultivars were grown in climate chambers with three temperature regimes (day/night temperatures of 13/10, 18/15 and 23/20 °C) during grain filling. The temperature strongly influenced grain weight and protein content. Gluten quality measured by maximum resistance to extension (Rmax ) was highest in three cultivars grown at 13 °C. Rmax was positively correlated with the proportion of sodium dodecyl sulfate-unextractable polymeric proteins (%UPP). The proportions of ω-gliadins and D-type low-molecular-weight glutenin subunits (LMW-GS) increased and the proportions of α- and γ-gliadins and B-type LMW-GS decreased with higher temperature, while the proportion of high-molecular-weight glutenin subunits (HMW-GS) was constant between temperatures. The cultivar Berserk had strong and constant Rmax between the different temperatures. Constant low temperature, even as low as 13 °C, had no negative effects on gluten quality. The observed variation in Rmax related to temperature could be explained more by %UPP than by changes in the proportions of HMW-GS or other gluten proteins. The four cultivars responded differently to temperature, as gluten from Berserk was stronger and more stable over a wide range of temperatures.

Phosphorus recycling by profunda quagga mussels (Dreissena rostriformis bugensis) in Lake Michigan

Abstract The effects of dreissenid mussels on plankton abundance and nutrient cycling in shallow, productive waters of the Great Lakes have been well-documented, but the effects of their more recent expansion into offshore regions have received much less attention. Understanding quagga mussel impact on Lake Michigan's phosphorus (P) fluxes is critical in assessing long-term implications for nutrient cycling and energy flow. In this study, P excretion and egestion rates were determined for mussels in the hypolimnion of Lake Michigan. Constant low temperatures and limited food supply contributed to a lower basal P excretion rate in profunda quagga mussels compared to the shallow phenotype. The P excretion:egestion ratio was approximately 3:2, highlighting the need to consider both of these pathways when assessing the effect of these filter feeders on nutrient dynamics. Total dissolved P (TDP) excretion rates ranged from 0.0002 to 0.0124 μmol mgDW − 1 d − 1 , soluble reactive P (SRP) excretion rates ranged from 0.0002 to 0.0061 μmol mgDW − 1 d − 1 , and particulate P (PP) egestion rates (feces + pseudofeces) ranged from 0.0007 to 0.0269 μmol mgDW − 1 d − 1 . The ability of profunda mussels to alter P cycling dynamics is reflected in an increased hypolimnetic dissolved:particulate P ratio and the disappearance of the benthic nepheloid layer. On an areal basis, mussel P recycling rates are up to 11 times greater than P settling rates as determined by sediment traps, suggesting that mussel grazing has resulted in an increased delivery rate of P to the deep benthos and a shorter P residence time in the water column.

Mixed Convection Heat Transfer inside a Square Cavity Filled with Cu-water Nanofluid

In the present study, mixed convection heat transfer inside a square cavity filled with Cu-water nanofluid has been investigated numerically. The bottom wall of the cavity is maintained at a constant high temperature while the vertical sidewalls are assumed to be at a constant low temperature. The top wall of the cavity is insulated and moving at a constant velocity. Galerkin finite element method has been employed to solve the continuity, momentum and energy balance equations for the present problem. Analysis of thermal and flow fields inside the cavity has been analysed in terms of isotherms, streamlines and heatlines for a wide range of the Richardson number and solid volume fraction of the nanoparticle. Particular attention was paid to the case of pure mixed convection case with the Richardson No being equal to 1 for various combinations of natural convection and forced convection effects. The heat transfer performance of the system has been analysed in terms of average Nusselt number over the heated wall for various parameters. The present study shows that the distribution of streamline, isothermal lines and heatlines are very sensitive to Richardson number. The present study also shows that larger heat transfer rates can be achieved with nanofluid than the base fluid for all conditions.

Effects of constant low temperature on cold resistance of different strains Polygonatum odoratum

In this paper, the five strains of Polygonatum odoratum were used as the experimental materials to test the supercooling point, freezing point, the degree of supercooling, the transition stage time, cooling time and water composition of the plant tissue. The cold resistance of P. odoratum was analyzed with the Gray Correlation Method. The results showed that the cold resistances of the five strains of P. odoratum were different, and the water content of plant tissue had some relevance with freezing point and supercooling point, whereas, it could not be measured when the moisture content was too low. The order of cold resistance of the five strains of P. odoratum was ZJCY, DYYZ, XYYZ, CYYZ and JZ I.

Germination of seeds of Avena fatua L. under different storage conditions

Storage conditions have a strong influence on the germination of seeds of &lt;em&gt;Avena fatua&lt;/em&gt; L, especially at variable conditions, the germination decreased. Seeds stored at a constant low temperature maintained the germination capability for 5 years. Under greenhouse conditions, seeds matured and germinated more rapidly comparing to field conditions, but individuals from these seeds were weaker and produced fewer seeds. The higher temperature in the greenhouse accelerated the development and maturing of plants. Field emergence varied depending on seed storage conditions, sample, further reproduction, and weather conditions. It was observed that individual specimens of &lt;em&gt;A. fatua&lt;/em&gt; were able to form ripe seeds with high thousand grain mass (TGM), regardless of the occurrence of fungal diseases. The knowledge of the biology of &lt;em&gt;A. fatua&lt;/em&gt; is very important due to its status as a restricted weed in certified seed of crop plants.

Isothermal DNA amplification strategies for duplex microorganism detection

A valid solution for micro-analytical systems is the selection of a compatible amplification reaction with a simple, highly-integrated efficient design that allows the detection of multiple genomic targets. Two approaches under isothermal conditions are presented: recombinase polymerase amplification (RPA) and multiple displacement amplification (MDA). Both methods were applied to a duplex assay specific for Salmonella spp. and Cronobacter spp., with excellent amplification yields (0.2–8.6·108 fold). The proposed approaches were successfully compared to conventional PCR and tested for the milk sample analysis as a microarray format on a compact disc (support and driver). Satisfactory results were obtained in terms of resistance to inhibition, selectivity, sensitivity (101–102CFU/mL) and reproducibility (below 12.5%). The methods studied are efficient and cost-effective, with a high potential to automate microorganisms detection by integrated analytical systems working at a constant low temperature.

Natural Convection Heat Transfer in a Cubic Cavity Submitted to Time-Periodic Sidewall Temperature

The laminar unsteady natural convection in a cubic cavity is comprehensively studied here using a high accuracy temporal-spatial pseudospectral method. In this study, the cavity is filled with air and one of its sidewalls is submitted to sinusoidally varying temperature, while constant lower temperature is imposed on the opposing sidewall and other sidewalls are adiabatic. Computations are performed to explore the effects of several influential factors on the fluid flow patterns and heat transfer performances within the cavity, including Rayleigh number and the amplitude and period of pulsating sidewall temperature. Numerical results reveal that the heat transfer enhancement is complexly determined by the above influential factors, and the heat transfer resonance is observed in the case of a large Rayleigh number and amplitude of pulsating sidewall temperature. The three-dimensional effects on fluid flow patterns and heat transfer are discussed. Finally, the backward heat transfer is quantitatively studied.

Research on Vertical Distribution of Water Temperature in Different Regulation Reservoirs

The vertical distribution of the reservoir water temperature depends on the scale of the reservoir, regulation manners, as well as the hydrological and geological conditions near reservoir areas. Based on water temperature observation from three different regulation reservoirs, this paper analyses the vertical distribution of these reservoirs water temperature. The preliminary conclusions are: for multi-annual regulation reservoirs, the upper zones usually have stable temperature stratification structures, while the lower zones have constant low temperature; for annual regulation reservoirs, water temperature distribution changes with depth; for the daily regulation reservoirs with low water depths present mixed vertical distributions of water temperature.

The potential of selected macroalgal species for treatment of AMD at different pH ranges in temperate regions

The metal bioaccumulation potential of selected macroalgae species at different pH ranges was study for usage as part of a possible secondary passive acid mine drainage (AMD) treatment technology in algae ponds. Two separate studies were conducted to determine the suitability of macroalgae for passive treatment when metabolic processes in macrophytes and microorganisms in constructed wetlands decrease during winter months. In the field study, the bioconcentration of metals (mg/kg dry weight) measured in the benthic macroalgae mats was in the following order: site 1. Oedogonium crassum Al > Fe > Mn > Zn; site 2. Klebsormidium klebsii, Al > Fe > Mn > Zn; site 3. Microspora tumidula, Fe > Al > Mn > Zn and site 4. M. tumidula, Fe > Mn > Al > Zn. In the laboratory study, cultured macroalgae K. klebsii, O. crassum and M. tumidula isolated from the field sampling sites were exposed to three different pH values (3, 5 and 7), while bioaccumulation of the metals, Al, Fe, Mn and Zn and glutathione S-transferase (GST) activity were measured in the different selected algae species at a constant water temperature of 14 °C. Bioaccumulation of Al was the highest for O. crassum followed by K. klebsii and M. tumidula (p < 0.0001). From the study it was evident that the highest metal bioaccumulation occurred in the macroalgae O. crassum at all three tested pH values under constant low water temperature.

Effects of hormone treatment, light and temperatures on sprouting characteristics of Bupleurum chinense

Seeds of Bupleurum chinense cultivar, Zhongchai No. 1, were sowed in plastic pots which used the arable layer soil as the nursery bed and putted in the artificial climate incubator at various temperatures (15, 20, 25, 15-25 degrees C) and light (8,12 h) to germinate, respectively. The lower constant temperature (15 degrees ) and the higher constant temperature (25 "C) were not conducive to the sprouting characteristics of B. chinese. While they were able to enhance root activity to some extent; The seeding growth of B. chinese was significantly better in the variable temperature than correspondence in the constant temperature, significantly. The emergence speed, emergence index, vigor index and root activity of Bupleurum were improved under the 12 h of light-time, but the germination rate was not improved. The sprouting of Bupleurum's seeds could be improved to some extent by soaking with hormone, such as gibberellin, cytokinin, salicylic acid. Gibberellin promoted seeds' sprouting and seedings's root activity of Bupleurum, while salicylic acid increased the root activity of seeding. There is a significant influence of light, temperatures and hormone treatment on the germination of Zhongchai No. 1 seeds, and all three are remarkably interacted; It is beneficial to promote seed germination by the temperature (20 + 5) degrees C, lighting (8 h) and gibberellin concentration (10 x 10(-6)).

Effect of low temperature on hydration performance of the complex binder of silica fume-portland cement

By analyzing the mechanical properties, composition of hydrates, content of Ca(OH)2 and microstructure of the complex binder of silica fume-Portland cement, which cured at constant low temperatures(+5-−10 °C), the effect of different low temperatures on hydration performance of the complex binder at the age of 3, 7 days and 14 days was researched. Experimental results show that hydration processes of the complex binder can be restricted by low temperature. Reducing the curing temperature could cause compressive strength and flexural strength of the complex binder to decrease significantly. The gradient difference between strength diminishes, content of Ca(OH)2 in hydrates reduces, and compactness of the microstructure weakens. Therefore mixing with silica fume can modify various performance indicators of the complex blinder, but reducing the curing temperature restricts the pozzolanic activity of silicon fume.