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1.
Hydrogen peroxide (H2O2) is an incompletely reduced metabolite of oxygen that has a diverse array of physiological and pathological effects within
living cells depending on the extent, timing, and location of its production. Characterization of the cellular functions of
H2O2 requires measurement of its concentration selectively in the presence of other oxygen metabolites and with spatial and temporal
fidelity in live cells. For the measurement of H2O2 in biological fluids, several sensitive methods based on horseradish peroxidase and artificial substrates (such as Amplex
Red and 3,5,3’5’-tetramethylbenzidine) or on ferrous oxidation in the presence of xylenol orange (FOX) have been developed.
For measurement of intracellular H2O2, methods based on dihydro compounds such as 2’,7’-dichlorodihydrofluorescein that fluoresce on oxidation are used widely
because of their sensitivity and simplicity. However, such probes react with a variety of cellular oxidants including nitric
oxide, peroxynitrite, and hypochloride in addition to H2O2. Deprotection reaction-based probes (PG1 and PC1) that fluoresce on H2O2-specific removal of a boronate group rather than on nonspecific oxidation have recently been developed for selective measurement
of H2O2 in cells. Furthermore, a new class of organelle-targetable fluorescent probes has been devised by joining PG1 to a substrate
of SNAP-tag. Given that SNAP-tag can be genetically targeted to various subcellular organelles, localized accumulation of
H2O2 can be monitored with the use of SNAP-tag bioconjugation chemistry. However, given that both dihydro- and deprotection-based
probes react irreversibly with H2O2, they cannot be used to monitor transient changes in H2O2 concentration. This drawback has been overcome with the development of redox-sensitive green fluorescent protein (roGFP)
probes, which are prepared by the introduction of two redox-sensitive cysteine residues into green fluorescent protein; the
oxidation of these residues to form a disulfide results in a conformational change of the protein and altered fluorogenic
properties. Such genetically encoded probes react reversibly with H2O2 and can be targeted to various compartments of the cell, but they are not selective for H2O2 because disulfide formation in roGFP is promoted by various cellular oxidants. A new type of H2O2-selective, genetically encoded, and reversible fluorescent probe, named HyPer, was recently prepared by insertion of a circularly
permuted yellow fluorescent protein (cpYFP) into the bacterial peroxide sensor protein OxyR. 相似文献
2.
We classify mathematical models that can be used to describe photosynthetic oscillations using ideas from nonlinear dynamics, and discuss potential mechanisms for photosynthetic oscillations in the context of this classification. We then turn our attention to recent experiments with leaves transferred to a low CO2 atmosphere which revealed stochastic oscillations with a period of a few seconds. Rubisco is the enzyme that takes both CO2 and O2 as substrates correspondingly for photosynthetic assimilation and for photorespiration. Photosynthesis depletes CO2 and produces O2 while respiration and photorespiration work in the opposite direction, so the product of one process becomes the reactant of the other coupled process. We examine the possibility of oscillations of CO2 and O2 in the leaf in relation to photorespiration. We suggest that in the cell, oscillations with a period of a few seconds, corresponding to the time between photosynthetic CO2 fixation and photorespiratory CO2 release, underlie the dynamics of metabolism in C3 plants. 相似文献
3.
Uri Y Levine Tracy K Teal G Philip Robertson Thomas M Schmidt 《The ISME journal》2011,5(10):1683-1691
Agriculture has marked impacts on the production of carbon dioxide (CO2) and consumption of methane (CH4) by microbial communities in upland soils—Earth''s largest biological sink for atmospheric CH4. To determine whether the diversity of microbes that catalyze the flux of these greenhouse gases is related to the magnitude and stability of these ecosystem-level processes, we conducted molecular surveys of CH4-oxidizing bacteria (methanotrophs) and total bacterial diversity across a range of land uses and measured the in situ flux of CH4 and CO2 at a site in the upper United States Midwest. Conversion of native lands to row-crop agriculture led to a sevenfold reduction in CH4 consumption and a proportionate decrease in methanotroph diversity. Sites with the greatest stability in CH4 consumption harbored the most methanotroph diversity. In fields abandoned from agriculture, the rate of CH4 consumption increased with time along with the diversity of methanotrophs. Conversely, estimates of total bacterial diversity in soil were not related to the rate or stability of CO2 emission. These combined results are consistent with the expectation that microbial diversity is a better predictor of the magnitude and stability of processes catalyzed by organisms with highly specialized metabolisms, like CH4 oxidation, as compared with processes driven by widely distributed metabolic processes, like CO2 production in heterotrophs. The data also suggest that managing lands to conserve or restore methanotroph diversity could mitigate the atmospheric concentrations of this potent greenhouse gas. 相似文献
4.
Claire M. Fraser Roger Greguski Barbara Eddy J. Craig Venter 《Journal of cellular biochemistry》1983,21(3):219-231
The combination of immunological advances with membrane receptor research has promoted rapid progress in the molecular characterization of neurotransmitter receptor molecules. We have to date produced monoclonal antibodies to β1-, β2-, and β1-adrenergic, D2-dopaminergic, and muscarinic receptors. In addition we have discovered that some allergic respiratory disease patients possess circulating autoantibodies to β2-adrenergic receptors. These antireceptor antibodies in conjunction with specific receptor affinity reagents have allowed us to isolate, purify, and begin to characterize α- and β-adrenergic, dopaminergic, and muscarinic receptors. For example, immunoprecipitation of turkey erythrocyte β1 receptors with monoclonal antibodies yields a single polypeptide Mr 65–70 K. In contrast, purification of β2-adrenergic receptors using either autoantibodies or monoclonal antibodies yields a receptor species with a subunit of Mr 55–59 K. Autoantibodies to β2 receptors demonstrate a 50–100% homology among β2 receptors from humans to rats, whereas monoclonal antibody FV-104 recognizes a determinant in the ligand binding site of all β1 and β2 receptors tested to date. These data suggest that β1- and β2-adrenergic receptors may have evolved from a common ancestor, perhaps by gene duplication. 相似文献
5.
Rausch Felix Schicht Martin Bräuer Lars Paulsen Friedrich Brandt Wolfgang 《Journal of molecular modeling》2014,20(11):1-12
The prospects of a control for a novel gallium nitride pseudo-halide vapor phase epitaxy (PHVPE) with HCN were thoroughly analyzed for hydrocarbons–NH3–Ga gas phase on the basis of quantum chemical investigation with DFT (B3LYP, B3LYP with D3 empirical correction on dispersion interaction) and ab-initio (CASSCF, coupled clusters, and multireference configuration interaction including MRCI+Q) methods. The computational screening of reactions for different hydrocarbons (CH4, C2H6, C3H8, C2H4, and C2H2) as readily available carbon precursors for HCN formation, potential chemical transport agents, and for controlled carbon doping of deposited GaN was carried out with the B3LYP method in conjunction with basis sets up to aug-cc-pVTZ. The gas phase intermediates for the reactions in the Ga-hydrocarbon systems were predicted at different theory levels. The located π-complexes Ga…C2H2 and Ga…C2H4 were studied to determine a probable catalytic activity in reactions with NH3. A limited influence of the carbon-containing atmosphere was exhibited for the carbon doping of GaN crystal in the conventional GaN chemical vapor deposition (CVD) process with hydrocarbons injected in the gas phase. Our results provide a basis for experimental studies of GaN crystal growth with C2H4 and C2H2 as auxiliary carbon reagents for the Ga-NH3 and Ga-C-NH3 CVD systems and prerequisites for reactor design to enhance and control the PHVPE process through the HCN synthesis. 相似文献
6.
《Inorganica chimica acta》1988,147(1):33-43
Complexes of Ru(II) and Ru(III) with the bidentate ligand diphenylphosphinoacetic acid (POH) are reported. The ligand POH reacts with RuCl2(PPh3)3 in a 1:3 ratio to give a five-coordinate complex of composition Ru(PO)2(POH) with complete displacement of PPh3. In a 1:2 ratio however the complex Ru(PO)2(PPh3) is formed. The reaction of POH with RuCl2(DMSO)4 in a 2:1 ratio afforded a yellow complex of composition HRu(PO)2Cl(DMSO). In a 3:1 ratio of POH to RuCl2(DMSO)4 however, the complex HRu(PO)3 was obtained. Neutral complexes of the composition Ru(PO)2Cl(AsPh3) and Ru(PO)3 were obtained by the reaction of RuCl3(AsPh3)2·MeOH with POH in 1:2 and 1:3 mole ratios in acetone solution, respectively. A dimeric chloro bridged complex of composition [Ru(PO)2Cl]2 was obtained on reaction of RuCl33H2O with POH in methanol. The complexes have been characterized on the basis of elemental analysis 1H, 13C{1H} and 31P{1H} NMR, EPR and electrochemical studies.The square pyramidal complexes 1 and 2 undergo facile addition reactions with CO, H2, PPh3 and DMSO to form octahedral species. The redox potentials RuIII/RuII of the complexes become more positive with an increase in the π-acidity of the ligand coordinated to the metal ion. 相似文献
7.
Water culture, growth chamber, greenhouse and field experiments were conducted to compare the effect of NH4−N and NO3−N on yield and N uptake of rapeseed (Brassica campestris L.). In water culture, the yields of 28-day old rapeseed plants grown at 14 μg N ml−1 were double with NO3 compared to NH4, but N uptake was little affected. There was no such effect when concentration was reduced to 3.5 or 7 μg N ml−1. The yield and N uptake of 26-day old rapeseed grown on six soils (pH 4.6 to 6.5) in pots in a growth chamber were much greater
with NO3 than with NH4, although N concentration was more in the NH4- than the NO3-grown plants. In a greenhouse experiment with rapeseed grown on 12 potted soils, the N uptake of applied N was greater with
NO3 than with NH4 on all soils. Averages were 63% with NH4 and 78% with NO3. However, NH4-fixation capacities of the soils were only weakly correlated with yield from the two sources of N (r=0.48) and the relation
was similar with N uptake. In contrast to the behavior of water culture, growth chamber and greenhouse experiments, the 33
field experiments did not show consistent difference in seed yield with NH4 and NO3 applied at time of seeding. In nine field experiments where band application was used for Ca(NO3)2, (NH4)2 SO4, NH4 NO3, yield tended to be greatest for (NH4)2SO4. However, in 19 experiments on acid soils with and without lime, yields in most cases were similar with (NH4)2SO4 and NH4 NO3. Nitrification inhibitors were added to spring banded NH4-based fertilizers in five experiments, but the yields were not influenced.
Scientific Paper No. 558, Lacombe Research Station, Agriculture Canada. 相似文献
8.
The nonenzymatic reaction of glyoxylate and H2O2 was measured under physiological conditions of the pH and concentrations of reactants. The reaction of glyoxylate and H2O2 was secondorder, with a rate constant of 2.27 l mol-1 s-1 at pH 8.0 and 25° C. The rate constant increased by 4.4 times in the presence of Zn2+ and doubled at 35°C. We propose a mechanism for the reaction between glyoxylate and H2O2. From a comparison of the rates of H2O2 decomposition by catalase and the reaction with glyoxylate, we conclude that H2O2 produced during glycolate oxidation in peroxisomes is decomposed by catalase but not by the reaction with glyoxylate, and that photorespiratory CO2 originates from glycine, but not from glyoxylate, in C3 plants. Simulation using the above rate constant and reported kinetic parameters leads to the same conclusion, and also makes it clear that alanine is a satisfactory amino donor in the conversion of glyoxylate to glycine. Some serine might be decomposed to give glycine and methylene-tetrahydrofolate; the latter is ultimately oxidized to CO2. In the simulation of the glycolate pathway of Euglena, the rate constant was high enough to ensure the decarboxylation of glyoxylate by H2O2 to produce photorespiratory CO2 during the glycolate metabolism of this organism.Abbreviations Chl
chlorophyll
- GGT
glutamate: glyoxylate aminotransferase (EC 2.6.1.4)
- Hepes
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- SGT
serine: glyoxylate aminotransferase (EC 2.6.1.45)
This is the ninth in a series on the metabolism of glycolate in Euglena gracilis. The eighth is Yokota et al. (1982) 相似文献
9.
Erich Kessler 《Archives of microbiology》1973,93(2):91-100
Summary The effect of anaerobic (N2+CO2) pre-incubation in the dark on photosynthetic reactions (O2 evolution, measured manometrically and with the oxygraph; fluorescence; and photoproduction of H2, measured with the mass spectrometer) was studied in algae with hydrogenase (strains of Chlorella fusca, C. kessleri, C. vulgaris f. tertia, and Ankistrodesmus braunii) and in algae without hydrogenase (strains of Chlorella vulgaris, C. saccharophila, and C. minutissima).The inhibition by anaerobic incubation of photosynthetic O2 evolution is much stronger in algae without hydrogenase than it is in algae with hydrogenase. The effect of anaerobiosis is most pronounced at rather low light intensity (about 1000 lux), in acid medium (pH 4), and after prolonged anaerobic incubation in the dark (about 20 h). These results indicate that the presence of hydrogenase might be ecologically advantageous for algae under certain conditions.Chlorophyll fluorescence showed the fastest response to anaerobic incubation, and the most pronounced difference between algae with and without hydrogenase. After only 30 min under N2+CO2, fluorescence in algae with hydrogenase starts with a peak and decreases within 10 to 20 sec to a rather low steady-state level which is only slightly higher than that found under aerobic conditions. In algae without hydrogenase, fluorescence is rather low during the first 1 to 2 sec and then rises to a higher steady-state level which is much higher than that of the aerobic controls. This indicates an inhibition due to anaerobiosis of photosystem II in algae without hydrogenase.Algae with hydrogenase can react in different ways during the first minutes of illumination. In some cases there is an immediate photoproduction of H2, which is followed after a few minutes by photosynthetic O2 evolution; in other algae there is a simultaneous production of H2 and O2 from the very beginning; in a few experiments there was no photoproduction of H2 at all, and in this case there was no photosynthetic O2 evolution either. Thus, photoproduction of H2 seems to be the process which normally enables algae with hydrogenase to oxidise and thereby activate their photosynthetic electron transport system after anaerobic incubation.A mass spectrometric search for nitrogen fixation (using N2 and acetylene) in eucaryotic green algae gave negative results, even with species containing hydrogenase and under anaerobic conditions. 相似文献
10.
Vibrational CD (VCD) spectra of a series of blocked linear, alternating D - and L -proline containing oligopeptides, dissolved in D2O and in CDCl3. are reported. For the Boc-LDL -Pro3 to Boc-DLDLDLDL-Pro8 oligomers. The VCD spectra in the amide I band is a positive couplet, opposite in sense to that obtained for (L -Pro)n oligomers. While this admits the possibility of their favoring a right-handed helical chain conformation, the amide I ir spectra for these dl oligomers in D2O indicate a mixed, apparently alternate, cis-trans conformation that prevents a simple conclusion. Their VCD in D2O evidence no narrowing and has a progressive loss in intensity (measured as Δ /A,) with an increase in chain length. In CDCl3a similar pattern of positive VCD couplets decreasing in intensity with length was seen, but their spectra are narrower. Their electronic CD (ECD) in the uv, also indicates a loss in intensity with increasing length. Oligomers with odd or even numbers of Pro residues have different ECD patterns, indicating that those spectra are strongly influenced by local contributions arising in the N-terminal groups. The VCD arises from dipolar and vibrational coupling of the amides in the helical structure. All the spectra are consistent with the chiral end groups leading to formation of an excess of one helical handedness. With an increase in length, the influence of this selectiveness is less and the overall CD measured decreases. © 1995 John Wiley & Sons, Inc. 相似文献
11.
Effect of growth and subsequent decomposition of blue-green algae on the transformation of iron and manganese in submerged soils 总被引:1,自引:0,他引:1
N2-fixing blue-green algae (Cyanobacteria), besides enriching soils with N and organic carbon, may modify a number of chemical and electro-chemical properties of the soils resulting in a change in availability of some micronutrient elements. Keeping this in view, an experiment was conducted to study the effects of growth and subsequent decomposition of blue-green algae on changes in the different forms of Fe and Mn in four soils under submerged condition. A mixed algal culture containing Anabaena, Nostoc, Cylindrospermum, and Tolypothrix was used as inoculum. It was allowed to grow for 2 months, after which the soils were sequentially extracted with (i) M NH4OAc (pH 7.0), (ii) M K4P2O7, (iii) 0.1 M NH2OH.HCl (pH 2.0), (iv) 0.2 M (NH4)2C2O4 (pH 3.0) and (v) 0.1 M ascorbic acid to obtain water-soluble plus exchangeable, organically bound, easily reducible, amorphous oxides-and crystalline oxides-bound forms of Fe and Mn, respectively, both during the growth as well as the subsequent in-situ decomposition of the algal biomass in soils. Iron and Mn in the extracts were estimated by atomic absorption spectrophotometry.The results showed that growth of blue-green algae in submerged rice soils caused a decrease in the NH4OAc-extractable forms of Fe and Mn with concomitant increases in all the other four determined forms of the elements. Such decreases and/or increases in different forms of Fe and Mn in soils were explained as being due to release of O2, addition of organic matter and liberation of extracellular organic compounds by the blue-green algae during their growth. The decomposition of algal biomass resulted in an increase in the NH4OAc-, K4P2O7- and (NH4)2C2O4-extractable forms of Fe and Mn with a simultaneous decrease in the NH2OH · HCl- and ascorbic acid-extractable forms. Development of strong reducing conditions and formation of organic acids with chelating properties were suggested as being the cause of the above changes. The implication of these changes in the forms of Fe and Mn for the Fe and Mn nutrition of rice plants were discussed. 相似文献
12.
Effects of temperature and oxygenavailability on greenhouse gas and nutrient dynamics in sediment of a eutrophic mid-boreal lake 总被引:4,自引:0,他引:4
Anu Liikanen Timo Murtoniemi Heikki Tanskanen Tero Väisänen Pertti J. Martikainen 《Biogeochemistry》2002,59(3):269-286
The effects of oxygen conditions and temperature on dynamics of greenhousegases (CH4, CO2, N2O) and nutrients(NH4
+, NO2
–+NO3
–, tot-P) were studied in sediment of hyper-eutrophic LakeKevätön, Finland. Undisturbed sediment cores were incubated at 6, 11,16, and 23 °C in a laboratory microcosm using a continuouswater flowtechnique with an oxic or anoxic water flow. The production of CO2increased with increasing temperature in both oxic (Q10 3.2 ±0.6) and anoxic (Q10 2.3 ± 0.4) flows. The release ofCH4 increased with temperature in anoxic conditions (Q102.3 ± 0.2), but was negligible with the oxic flow at all temperatures.The release of NH4
+ increased with temperature with the oxic and anoxic flows(Q10 2.4 ± 0.1). There was a net production of NO2
–, NO3
– and N2O with the oxic flow at temperatures below16 °C. The release of phosphorus was greater from the anoxicsediments and increased with temperature with both the anoxic (Q102.9 ± 0.5) and oxic (Q10 1.9 ± 0.1) flows. It isprobable that the temperature of boreal lakes and the associated oxygendeficiency will increase as the climate becomes warmer. Our experiments showedthat this change would increase the global warming potential of greenhousegasesreleased from sediments of eutrophic lakes predominately attributable to theincrease in the CH4 production. Furthermore, warming would alsoaccelerate the eutrophication of lakes by increasing release of phosphorus andmineral nitrogen from sediments, which further enhance CH4productionin sediments. 相似文献
13.
A study was conducted in a screen house in pots on a sandy loam soil deficient in Zn. Salinity was induced by adding 44, 88 and 132 me/l of chloride and sulphate salts in the saturation extract. To these treatments, 0, 5 and 10 ppm Zn were added as ZnSO4·7H2O or Zn-EDTA. The results indicated that the yield of soybean shoot was lowest at the highest salinity level and highest at the lowest level. Shoot yield improved markedly with Zn application. Both sources of Zn were equally effective in augmenting crop yields. Yields were low in Cl-salinity when compared with equivalent levels of SO4-salinity. Application of ZnSO4·7H2O produced higher yields in SO4-dominant salinity. Zinc content increased and Zn uptake decreased with increase in Cl-salinity regardless of Zn sources. In SO4-salinity, ZnSO4·7H2O did not influence the Zn content, but uptake was suppressed with increase in SO4-salinity. Increasing rates of SO4-salinity enhanced Zn content in the presence of Zn-EDTA. 相似文献
14.
The effects of thermo- and photoperiodicity on elongation growth and on endogenous level of gibberellins (GAs) in Begonia x hiemalis during various phases of the day-night cycle have been studied. Plant tissue was harvested during the day and night cycle
after temperature and photoperiodic treatments and analyzed for endogenous GAs using combined gas chromatography and mass
spectrometry. Elongation growth increased when the difference between day and night temperature (DIF = DT − NT) increased
from a negative value (−9.0 and −4.5°C) to zero and with increasing photoperiod from 8 to 16 h. When applied to the youngest
apical leaf, gibberellins A1, A4, and A9 increased the elongation of internodes and petioles. GA4 had a stronger effect on elongation growth than GA1 and GA9. In relative values, the effect of these GAs decreased when DIF increased from −9 to 0°C. The time of applying the GAs during
a day and night cycle had no effect on the growth responses. In general, endogenous levels of GA19 and GA20 were higher under negative DIF compared with zero DIF. The level of endogenous GA1 in short day (SD)-grown plants was higher under zero DIF than under negative DIF, but this relationship did not appear in
long day (LD)-grown plants. The main effects of photoperiod seem to be a higher level of GA19 and GA1 at SD compared with LD, whereas GA20 and GA9 show the opposite response to photoperiod. No significant differences in endogenous level of GA1, GA9, GA19, and GA20 were found for various time points during the diurnal day and night cycle. Endogenous GA20 was higher in petiole and leaf compared with stem, whereas there were no differences of GA1, GA9, and GA19 between plant parts. No clear relationship was found between elongation of internodes and petioles and levels of endogenous
GAs.
Received December 26 1996; accepted July 1, 1997 相似文献
15.
Brian L. Foster Kevin A. Tompkins R. Bruce Rutherford Hai Zhang Emily Y. Chu Hanson Fong Martha J. Somerman 《Birth defects research. Part C, Embryo today : reviews》2008,84(4):281-314
Inorganic phosphate (Pi) is abundant in cells and tissues as an important component of nucleic acids and phospholipids, a source of high‐energy bonds in nucleoside triphosphates, a substrate for kinases and phosphatases, and a regulator of intracellular signaling. The majority of the body's Pi exists in the mineralized matrix of bones and teeth. Systemic Pi metabolism is regulated by a cast of hormones, phosphatonins, and other factors via the bone‐kidney‐intestine axis. Mineralization in bones and teeth is in turn affected by homeostasis of Pi and inorganic pyrophosphate (PPi), with further regulation of the Pi/PPi ratio by cellular enzymes and transporters. Much has been learned by analyzing the molecular basis for changes in mineralized tissue development in mutant and knock‐out mice with altered Pi metabolism. This review focuses on factors regulating systemic and local Pi homeostasis and their known and putative effects on the hard tissues of the oral cavity. By understanding the role of Pi metabolism in the development and maintenance of the oral mineralized tissues, it will be possible to develop improved regenerative approaches. Birth Defects Research (Part C) 84:281–314, 2008. © 2008 Wiley‐Liss, Inc. 相似文献
16.
J. A. Bunce 《Photosynthetica》2012,50(3):395-400
The carbon dioxide concentration in free air carbon dioxide enrichment (FACE) systems typically has rapid fluctuations. In our FACE system, power spectral analysis of CO2 concentration measured every second with an open path analyzer indicated peaks in variation with a period of about one minute. I used open-top chambers to expose cotton and wheat plants to either a constant elevated CO2 concentration of 180 ??mol mol?1 above that of outside ambient air, or to the same mean CO2 concentration, but with the CO2 enrichment cycling between about 30 and 330 ??mol mol?1 above the concentration of outside ambient air, with a period of one minute. Three short-term replicate plantings of cotton were grown in Beltsville, Maryland with these CO2 concentration treatments imposed for 27-day periods over two summers, and one winter wheat crop was grown from sowing to maturity. In cotton, leaf gas-exchange measurements of the continuously elevated treatment and the fluctuating treatment indicated that the fluctuating CO2 concentration treatment consistently resulted in substantial down-regulation of net photosynthetic rate (P N) and stomatal conductance (g s). Total shoot biomass of the vegetative cotton plants in the fluctuating CO2 concentration treatment averaged 30% less than in the constantly elevated CO2 concentration treatment at 27 days after planting. In winter wheat, leaf gas-exchange measurements also indicated that down-regulation of P N and g s occurred in flag leaves in the fluctuating CO2 concentration treatment, but the effect was not as consistent in other leaves, nor as severe as found in cotton. However, wheat grain yields were 12% less in the fluctuating CO2 concentration treatment compared with the constant elevated CO2 concentration treatment. Comparison with wheat yields in chambers without CO2 addition indicated a nonsignificant increase of 5% for the fluctuating elevated CO2 concentration treatment, and a significant increase of 19% for the constant elevated treatment. The results suggest that treatments with fluctuating elevated CO2 concentrations could underestimate plant growth at projected future atmospheric CO2 concentrations. 相似文献
17.
A. G. Kisten’ I. K. Kurdish Z. T. Bega I. Yu. Tsarenko 《Applied Biochemistry and Microbiology》2006,42(3):278-283
We studied the effect of a clay mineral, palygorskite, on the physiological activity of Azotobacter chroococcum and the phosphate-mobilizing bacterium Bacillus subtilis, as well as their mixed cultures, under various oxygen supply conditions during the utilization of phosphorus from readily and poorly soluble compounds (K2HPO4 · 3H2O) and (Ca3(PO4)2), respectively. During cultivation of the bacteria in a nutrient medium with Ca3(PO4)2, the number of microorganisms was higher than that observed in a medium with K2HPO4. An increase in oxygen mass transfer in the nutrient medium was followed by a rise in the number of Bacillus subtilis cells and an inhibition of Azotobacter chroococcum growth. An addition of palygorskite (5 g/l) into the nutrient medium stimulated the growth of both bacteria and stopped the decreasing growth of Azotobacter chroococcum at high values of oxygen mass transfer. The number of Bacillus and, particularly, Azotobacter cells was two to five times lower in a mixed culture than in a monoculture. These differences were less significant during the cultivation of mixed cultures in medium with palygorskite. 相似文献
18.
Quantitation of vitamin D and its metabolites and their plasma concentrations in five species of animals 总被引:5,自引:0,他引:5
Chromatographic methods suitable for the resolution of 24,25-dihydroxyvitamin D3, 24,25-dihydroxyvitamin D2, 25-hydroxyvitamin D3-26,23 lactone, and 25,26-dihydroxyvitamin D2 are described. These four metabolites comigrated in high-pressure liquid chromatography on silicic acid columns developed in 11:89 isopropanol:hexane. Adequate resolution was achieved by subjecting the four-metabolite complex to high-pressure liquid chromatography column developed in 2:98 isopropanol:methylene chloride. This additional chromatographic step, coupled with modifications of assay procedures previously described, allowed for the estimation of plasma concentrations of vitamin D2, vitamin D3, 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, 24,25-dihydroxyvitamin D2, 24,25-dihydroxyvitamin D3, 25,26 dihydroxyvitamin D2, 25,26-dihydroxyvitamin D3, 25-hydroxyvitamin D3-26,23 lactone, and 1,25-dihydroxyvitamin D (1,25-dihydroxyvitamin D2 plus 1,25-dihydroxyvitamin D3). The samples automatically were introduced onto the high-pressure liquid chromatography columns with a Waters 710A “intelligent” processor. The metabolites were automatically collected with the aid of a programmable timer that advanced a fraction collector at predetermined intervals. The assays were used to determine the plasma vitamin D and vitamin D metabolite concentrations in five species of adult farm animals. 相似文献
19.
覆盖材料和沟垄比对土壤水分和紫花苜蓿干草产量的影响 总被引:4,自引:0,他引:4
为寻求半干旱黄土高原区种植紫花苜蓿的适宜覆盖材料和最佳沟垄比,采用完全随机设计布置大田试验,以传统平作为对照,研究不同垄覆盖材料(土壤结皮、生物可降解地膜和普通地膜)和不同沟垄比(沟宽:垄宽分别为60∶30、60∶45和60∶60,单位是cm)对土壤水分和紫花苜蓿干草产量等的影响。结果表明:通过对2012年和2013年紫花苜蓿生育期降雨量统计,2a平均值显示,无效降雨次数(53次)大于有效降雨次数(27次),无效降雨对总降雨量的贡献率(19%)小于有效降雨(81%)。就紫花苜蓿全生育期而言,与平作相比,SR_(30)、SR_(45)、SR_(60)、BMR_(30)、BMR_(45)、BMR_(60)、CMR_(30)、CMR_(45)和CMR_(60)(SR、BMR和CMR分别代表土垄、生物可降解膜垄和普通膜垄,下标分别表示垄宽为30、45cm和60cm)连续2a的平均根层(0—140 cm)土壤贮水量分别提高12.8、19.2、24.4、26.0、30.7、40.5、29.9、37.1 mm和47.7 mm。垄沟集雨种植第1年龄和第2年龄紫花苜蓿根层没有出现明显干层。与平作相比,SR_(30)、SR_(45)和SR_(60)的连续2a紫花苜蓿平均实际干草产量分别降低3%、8%和13%,WUE分别提高52%、58%和55%;BMR_(30)、BMR_(45)、BMR_(60)、CMR_(30)、CMR_(45)和CMR_(60)的连续2a紫花苜蓿平均实际干草产量分别提高14%、12%、7%、17%、19%和9%,WUE分别提高49%、62%、59%、51%、67%和56%。当紫花苜蓿生育期降雨量为380.7—427.6 mm和沟垄比为60 cm∶35—36 cm时,生物可降解膜垄和普通膜垄的紫花苜蓿实际干草产量达到最大值,为该地区垄沟集雨种植紫花苜蓿提供参考。 相似文献
20.
ALBERTO VICENTINI JANET C. BARBER SANDRA S. ALISCIONI LILIANA M. GIUSSANI ELIZABETH A. KELLOGG 《Global Change Biology》2008,14(12):2963-2977
At high temperatures and relatively low CO2 concentrations, plants can most efficiently fix carbon to form carbohydrates through C4 photosynthesis rather than through the ancestral and more widespread C3 pathway. Because most C4 plants are grasses, studies of the origin of C4 are intimately tied to studies of the origin of the grasses. We present here a phylogeny of the grass family, based on nuclear and chloroplast genes, and calibrated with six fossils. We find that the earliest origins of C4 likely occurred about 32 million years ago (Ma) in the Oligocene, coinciding with a reduction in global CO2 levels. After the initial appearance of C4 species, photosynthetic pathway changed at least 15 more times; we estimate nine total origins of C4 from C3 ancestors, at least two changes of C4 subtype, and five reversals to C3. We find a cluster of C4 to C3 reversals in the Early Miocene correlating with a drop in global temperatures, and a subsequent cluster of C4 origins in the Mid‐Miocene, correlating with the rise in temperature at the Mid‐Miocene climatic optimum. In the process of dating the origins of C4, we were also able to provide estimated times for other major events in grass evolution. We find that the common ancestor of the grasses (the crown node) originated in the upper Cretaceous. The common ancestor of maize and rice lived at 52 ± 8 Ma. 相似文献