Q10 Factor Research Articles

Estimation of daily soil CO2 flux using a single-time-point measurement

Information on soil CO2 emissions can be used in conjunction with data for C inputs from plants to estimate the soil C balance. Many studies assume a single-time-point measurement of soil CO2 flux taken in a day (Fh) is equal to its daily average value (Fd), which could result in over- or underestimation. A model using Fh, the temperature at the time the Fh is measured (Th), daily average temperature (Td) and Q10 factor to predict Fd was tested with extensive measurements of soil CO2 flux, temperature and moisture over 60 d from various treatments (no-till wheat, summer fallow and stubble, etc.) on a Swinton silt loam near Swift Current, Saskatchewan, Canada. A distinct hysteresis between flux and soil moisture was observed following rain events. Therefore, data for five rainy days were excluded from the analysis as the model does not consider the effect of hysteresis. Calculated Q10 factors were 1.86 and 1.54 for soil (Ts) and air (Ta) temperatures, respectively. The model using either Ts or Ta improved prediction of Fd in both calibration (49 d) and validation (6 d) datasets compared with Fh. Values of Fh measured in 6 yr were higher than modelled values of Fd in 96% of the 1602 treatment-days, hence if Fh is assumed to be equal to Fd, the averaged overestimation would be 17%.Key words: Soil CO2 flux, Q10 factor, temperature

Carbon dioxide efflux in a rhodic hapludox as affected by tillage systems in southern Brazil

Agricultural soils can act as a source or sink of atmospheric C, according to the soil management. This long-term experiment (22 years) was evaluated during 30 days in autumn, to quantify the effect of tillage systems (conventional tillage-CT and no-till-NT) on the soil CO2-C flux in a Rhodic Hapludox in Rio Grande do Sul State, Southern Brazil. A closed-dynamic system (Flux Chamber 6400-09, Licor) and a static system (alkali absorption) were used to measure soil CO2-C flux immediately after soybean harvest. Soil temperature and soil moisture were measured simultaneously with CO2-C flux, by Licor-6400 soil temperature probe and manual TDR, respectively. During the entire month, a CO2-C emission of less than 30 % of the C input through soybean crop residues was estimated. In the mean of a 30 day period, the CO2-C flux in NT soil was similar to CT, independent of the chamber type used for measurements. Differences in tillage systems with dynamic chamber were verified only in short term (daily evaluation), where NT had higher CO2-C flux than CT at the beginning of the evaluation period and lower flux at the end. The dynamic chamber was more efficient than the static chamber in capturing variations in CO2-C flux as a function of abiotic factors. In this chamber, the soil temperature and the water-filled pore space (WFPS), in the NT soil, explained 83 and 62 % of CO2-C flux, respectively. The Q10 factor, which evaluates CO2-C flux dependence on soil temperature, was estimated as 3.93, suggesting a high sensitivity of the biological activity to changes in soil temperature during fall season. The CO2-C flux measured in a closed dynamic chamber was correlated with the static alkali adsorption chamber only in the NT system, although the values were underestimated in comparison to the other, particularly in the case of high flux values. At low soil temperature and WFPS conditions, soil tillage caused a limited increase in soil CO2-C flux.

How is the Temperature Sensitive (TS) Reaction of F1-ATPase Coupled with its Rotation?

F1-ATPase (F1) is a rotary molecular motor in which γ subunit rotates against α3β3 cylinder. So far, 80° and 40° substeps in rotation of F1 have been observed, and kinetic analysis has shown that the 80° substep is initiated by concomitant ATP binding and ADP release, and the 40° substep occurs after ATP hydrolysis and inorganic phosphate release. Temperature sensitive (TS) reaction of F1 has found recently at the ATP binding angle at the temperature below 10 °C, and it has been suggested to correspond to ADP release (Watanabe et al., EMBO report 2008). In this study, TS reaction of βE190D mutant, that has much slower ATP hydrolysis rate than wild type, was found below 20 °C. Q10 factor of TS reaction of βE190D mutant was 16, that is comparable to that of wild type. Previous single-molecule rotation observations of the hybrid F1 that has only one mutant β subunit, α3β(WT)2β(E190D)γ have shown that the β subunit binds ATP at 0°, cleaves ATP at 200°, and release ADP and inorganic phosphate after cleavage of ATP (Ariga et al., NSMB 2007). In contrast to our expectation, observation of hybrid F1 α3β(WT)2β(E190D)γ rotation at 18 °C has revealed that TS reaction occurs at ATP binding angle(0°) to mutated β subunit. Furthermore, simultaneous observation at the video rate (30 frames per seconds) showed that Cy3-ATP bindings and steps in rotation occur concomitantly. We will discuss about the reaction schemes that can explain these results.

Oxidative stability and shelf-life evaluation of selected culinary oils

Four out of eight ‘healthier’ oils—namely, almond oil, avocado oil, hazelnut oil and macadamia nut oil—studied were rich sources of monounsaturated fatty acids like olive oil. Grape seed oil, rice barn oil (marketed recently), toasted sesame oil and walnut oil contained high levels of essential fatty acids. The order of oxidative stability determined by Rancimat measuring of the induction period at four temperatures (90°C, 100°C, 110°C, and 120°C) was found to be macadamia oil > rice bran oil ≈ toasted sesame oil > avocado oil > almond oil > hazelnut oil > grape seed oil > walnut oil. High-level monounsaturated fatty acid oils gave a linear relationship between 100 times the reciprocal of the induction period against the total unsaturated fatty acid content obtained as%C18:2 + 0.08 x%C18:1 + 2.08 x%C18:3, while the polyunsaturated fatty acid oils gave an exponential relationship. In the case of rice bran and hazelnut oils, shelf-life prediction from the extrapolation of the Arrhenius plots and the Q10 factors was compared well with that of storage time given by the oil producers. In the cases of the other oils (with an exception of macadamia nut oil), the predicted shelf-lives were significantly lower than that of the storage times; especially, walnut oil (very prone to oxidation) gave 15–20 times lower shelf-life than the best-before storage life.

Temperature and dates of male meiosis in trees

A review of methods is given, including conventional and non-linear heat sum methods, statistical considerations and benefit of graphic methods. Actual dates in 1968-71 of onset of meiotic stages of 11 tree species growing in natural conditions at Punkaharju and Rovaniemi, Finland, are presented. It is shown that no abrupt thermal threshold is necessary for the start of meiosis in the spring. The dormancy period has a great synchronizing effect on the progress of Larix meioses when different species or individuals of the same species are compared. It is suggested that the halt in the development of a plant at low temperatures, e.g., during meiosis, is caused by drying up of cell (PMC) protoplasts due to onset of freezing. Premises for finding the zero point of generative development after winter dormancy are evaluated. Disturbances in the flowering cycle of trees are discussed. Q10 factors are shown to be of little avail as delineators of the meiotic development.

Temperature‐sensitive reaction intermediate of F1‐ATPase

F1-ATPase is a rotary molecular motor that makes 120° stepping rotations, with each step being driven by a single-ATP hydrolysis. In this study, a new reaction intermediate of F1-ATPase was discovered at a temperature below 4°C, which makes a pause at the same angle in its rotation as when ATP binds. The rate constant of the intermediate reaction was strongly dependent on temperature with a Q10 factor of 19, implying that the intermediate reaction accompanies a large conformational change. Kinetic analyses showed that the intermediate state does not correspond to ATP binding or hydrolysis. The addition of ADP to the reaction mixture did not alter the angular position of the intermediate state, but specifically lengthened the time constant of this state. Conversely, the addition of inorganic phosphate caused a pause at an angle of +80° from that of the intermediate state. These observations strongly suggest that the newly found reaction intermediate is an ADP-releasing step.

Influência da temperatura na respiração, produção de etileno e longevidade de inflorescências de esporinha

O objetivo do trabalho foi avaliar a influência da temperatura na respiração e produção de etileno em inflorescências de esporinha (Consolida ajacis), e se a produção de CO2 poderia ser utilizada como indicador da longevidade das flores. As hastes foram colhidas, colocadas em vasos e armazenadas em temperatura de 5, 10, 15, 20, 25, 30, 35, e 40ºC até a completa senescência das flores. Ocorreu variação temporal similar na respiração e produção de etileno em função da elevação da temperatura, com produção máxima de 1.854 mL CO2 kg-1 h-1 e de 11,28 mL C2H4 kg-1 h-1 a 30 ºC e 40 ºC, respectivamente. O fator Q10 da respiração entre 5 e 30 ºC oscilou entre os valores de 1,11 e 2,89, semelhante a outros produtos hortícolas. A longevidade das flores foi inversamente proporcional ao aumento da temperatura entre 5 e 30 ºC. A vida de vaso estimada da esporinha foi reduzida de 11,9 para 4,1 dias com o aumento da temperatura de armazenamento de 5 para 30 ºC. A longevidade das flores mantidas a 35 e 40 ºC foi semelhante a das flores armazenadas a 30 ºC.

Role of the seagrass Thalassia testudinum as a source of chromophoric dissolved organic matter in coastal south Florida

Seagrasses play a variety of important ecological roles in coastal ecosystems. Here we present evidence that seagrass detritus from the widespread species Thalassia testudinum is an important source of ocean color and a UV-protective substance in a low latitude coastal shelf region of the United States. The production and light-induced degradation of chromophoric (sunlight- absorbing) dissolved organic matter (CDOM) from T. testudinum was examined under field and con- trolled laboratory conditions to obtain data that could be used to estimate the contribution of sea- grass-derived CDOM to the coastal pool. The laboratory studies measured the temperature depen- dence and photodegradation of the spectral (UV-visible, fluorescence) and molecular mass properties of CDOM produced during the degradation of T. testudinum detritus. The rate of CDOM production is temperature-dependent with rates doubling when temperature increases from 21.4 to 32.6°C. The magnitude of this increase is close to the widely observed Q10 factor for microbial decomposition, indicating that the CDOM production was likely microbially mediated. The absorption coefficients and fluorescence of CDOM from T. testudinum decreased on exposure to solar UV radiation (UVR) and the wavelength dependence was determined for this photobleaching process.

Temperature Controls on Diurnal Carbon Dioxide Flux

Carbon dioxide flux from the soil to the atmosphere is an important component of terrestrial C cycling, and accurate estimates of CO2–C fluxes are critical in estimating C budgets. Accurate estimation of daily C loss from infrequent measurements of CO2 flux requires characterization of the temporal variability associated with this processes. We investigated the relationships between diurnal CO2 flux and temperature at two locations, corresponding to two soil types (a sandy loam and a clay loam) in a residue covered no‐till corn (Zea mays L.)/soybean field (Glycine Max L. Merr.). Automated chambers provided hourly measurements of CO2 flux from 4 Mar. through 6 June 2000. Hourly soil temperature measurements were made at the surface and at the 0.05‐m depth, along with air temperature and soil water content measurements. Time series analysis showed that the temporal dynamics of CO2 flux were more closely related to air temperature than to soil temperature, perhaps because a substantial portion of the CO2 originated from surface residues. Exponential temperature correction algorithms (Q10) were evaluated using a range of Q10 factors applied to both air and soil temperatures. We found that a Q10 = 2 relationship when applied to a 0.05‐m soil temperature performed poorly in this regard, however, air temperature based Q10 relationships (Q10 = 1.5 or 1.25) performed better in that they reduced time‐of‐day estimation biases from 28 to <4%. Knowledge of the efficacy of temperature correction algorithms and application of the appropriate temperature measurements should improve the accuracy of cumulative C flux estimates from short‐term measurements.

Carbon isotope discrimination of arctic and boreal biomes inferred from remote atmospheric measurements and a biosphere‐atmosphere model

Estimating discrimination against 13C during photosynthesis at landscape, regional, and biome scales is difficult because of large‐scale variability in plant stress, vegetation composition, and photosynthetic pathway. Here we present estimates of 13C discrimination for northern biomes based on a biosphere‐atmosphere model and on National Oceanic and Atmospheric Administration Climate Monitoring and Diagnostics Laboratory and Institute of Arctic and Alpine Research remote flask measurements. With our inversion approach, we solved for three ecophysiological parameters of the northern biosphere (13C discrimination, a net primary production light use efficiency, and a temperature sensitivity of heterotrophic respiration (a Q10 factor)) that provided a best fit between modeled and observed δ13C and CO2. In our analysis we attempted to explicitly correct for fossil fuel emissions, remote C4 ecosystem fluxes, ocean exchange, and isotopic disequilibria of terrestrial heterotrophic respiration caused by the Suess effect. We obtained a photosynthetic discrimination for arctic and boreal biomes between 19.0 and 19.6‰. Our inversion analysis suggests that Q10 and light use efficiency values that minimize the cost function covary. The optimal light use efficiency was 0.47 gC MJ−1 photosynthetically active radiation, and the optimal Q10 value was 1.52. Fossil fuel and ocean exchange contributed proportionally more to month‐to‐month changes in the atmospheric growth rate of δ13C and CO2 during winter months, suggesting that remote atmospheric observations during the summer may yield more precise estimates of the isotopic composition of the biosphere.

Oxygen consumption in Oreochromis niloticus (L.) in relation to development, salinity, temperature and time of day

Oxygen consumption of Oreochromis niloticus at different stages of development was studied in relation to salinity, temperature and time of day, using a Warburg apparatus. The oxygen consumption of newly hatched (0–14 h) larvae was 3.40 μl O2 larva−1 h−1, of older yolk sac larvae 10.09 μl O2 larva−1 h−1, and of one‐month‐old fry 32.99 μl O2 larva−1 h−1. The QO2 values showed a decrease with development and growth, ranging from 21.2–26.0 μl O2 mg−1 h−1 in newly hatched larvae to 2.97 μl mg−1 h−1 in one‐month‐old fry. Changes in oxygen consumption occurred with salinity, the highest being at 17%o. Active larvae (12‐24 mm T.L.) showed a doubling of consumption with a 10° C rise in temperature, and their Q10 factor increased from 2.25 to 3.43 with increasing size. Day‐old yolk‐sac larvae, late yolk‐sac larvae (5 days old) and fry of 12 14 mm length all showed a depression in oxygen consumption at midnight followed by a dawn rise.

Origin and voltage dependence of asparagine-induced depolarization in intestinal cells of Xenopus embryo.

The kinetics and voltage dependence of asparagine (Asn)-induced depolarization in endoderm cells from Xenopus laevis embryos were analysed using current-clamp techniques. The depolarization is assumed to reflect the activation of an amino acid membrane carrier; it is accompanied by a slight increase in membrane resistance and cannot be explained by only the electrogenic character of the Asn carrier. It is proposed that the Asn depolarization arises, at least in part, from the decrease of the permeability ratio PK/PNa indirectly associated with the Na-coupled amino acid uptake. At room temperature (20-23 degrees C) the Asn response develops according to a single exponential function whose time constant is correlated with the final level of depolarization. Both amplitude and rise time of the depolarization are sensitive to variations of membrane potential and changes in Asn or Na external concentrations. Lowering the temperature decreases the amplitude of the Asn depolarization and increases its rise time with a Q10 factor of two; the kinetics remain of the Michaelis-Menten type, with a marked decrease in delta Emax and no change in Km. When the holding potential is altered by depolarizing and hyperpolarizing currents, the Asn response varies according to a bell-shaped characteristic presenting an optimum near the normal resting level. Membrane depolarizations induced by Na/K-pump inhibitors or high external K concentrations reduce the size of the Asn response; repolarizing the cell by current injection does not reverse the inhibitory effect of external K ions. Hyperpolarizing the membrane with a K-free Ringer solution increases the amplitude of the Asn response. In all these cases a decrease in delta Emax accounts for the apparent voltage sensitivity of the carrier mechanism. When induced by alterations of [K]o, an additional change in Km is observed, suggesting a K/Na-competitive inhibition of the Asn carrier. The results are discussed in terms of the amino acid carrier and passive membrane properties. It is suggested that the outward K-electrochemical gradient contributes an additional source of energy to the Na-dependent Asn uptake.

Spreading depression in elasmobranch cerebellum

Spreading depression (SD) occurs in the cerebellum of an elasmobranch fish, the skate (Raja erinacea, Raja ocellata). The elasmobranch cerebellum, because of its unique separation of granular form molecular layer, provides an excellent opportunity to study the characteristics of SD in two distinct neuronal populations. Both the DC potential shifts and changes in neuronal activity effected by SD were analyzed. The SD DC potential shifts in both layers closely resembled those in mammalian cerebral cortices. Consisting of a predominantly negative extracellular potential shift, they were typically 1--10 min in duration and reached 5--40 mV peak amplitudes. The largest negative shifts were found in the granular layer, without any consistent positive phases in the white matter, molecular, or granular layers. The SD propagated radially from surface electrical stimulation at 0.78 mm/min (+/- 0.16, n = 8) in the molecular layer and 0.43 mm/min (+/- 0.17, n = 8) in the granular layer at 15 degrees C. At 18 degrees C, the molecular layer propagatory velocity was 1.1 mm/min (+/- 0.12, n = 20) while, at 10 degrees C, it was 0.52 mm/min (+/- 0.21, n = 20), suggesting a temperature-dependent Q10 factor of 2. A profound depression of both spontaneous and evoked neuronal activity accompanied the DC potential shift. Activation of Purkinje cells antidromically, white matter, and granular layer neurons was typically abolished by the peak of the negative DC shift. However, a significant increase in granular layer excitability often followed the neuronal depression, remaining so far up to an hour. Repeated waves of SD sometimes occurred in the absence of neuronal recovery. A similar post-SD excitability increase was not seen in molecular layer neurons. Intracellular recordings from Purkinje cells revealed a spontaneous burst of action potentials at the onset of SD, closely followed by a depolarization of membrane potential from an average of -64 mV (+/- 12 mV, n = 3) to -11 mV (+/- 5 mV, n = 3).

Accelerated Stability Study of Metronidazole Infusion 100 ml

Metronidazole infusion had been prepared and studied under acceleration by heat at 37 and 50 °C temperatures. Physical and chemical evaluation had been carried out on 4th, 50th and 90th day, respectively. Chemical assay had been performed by UV light absorption spectroscopy. After 3 months stability data were analyzed by statistical regression analysis and plotted against time. It followed pseudo first order degradation kinetics. Rate constants were found out from this plot and set up in Arrhenious equation to find out the energy of activation. The rate constants were 14.1604 X 10-5 and 30.1 X 10-5 days-1 for 37 and 50 °C, respectively. According to Q10 method this value was used to determine the exact Q10 factor, which indicated its lower estimate value. Taking this lower value the expire dates were predicted for 5.3 yrs, 3.8 yrs, and 2.2 yrs, at 20 °C, 25 °C and 33 °C, respectively. These temperatures were the room temperatures of winter zone, Asian subcontinent and tropical zone, respectively. doi: 10.3329/taj.v18i2.3191 TAJ 2005; 18(2): 113-117