Simple chemical reaction systems with limit cycle behaviour

It is shown that for exhibiting limit cycle behaviour a two-component chemical reaction system has to involve at least three reactions among which one must be autocatalytic of the type 2X + … ? 3X + … Under this condition, possible candidates for chemical limit cycle systems are selected by postulating their steady state to be an instable focus. This procedure can be reduced to the selection of appropriate stoichiometric coefficients and is readily performed by a medium size computer. The result is quite a lot of limit cycle systems which are altogether simpler than, for example, the “Brusselator” with its number of four reactions. One of the results is briefly discussed.     

1H and 13C nuclear magnetic resonance spectra of the lipids in normal and SV 40 virus-transformed hamster embryo fibroblast membranes

Well resolved ¹H and ¹³C NMR spectra were obtained with normal and SV 40-transformed cell membranes. Estimation of the ratio of ¹³CT₂ values of the normal to transformed cell membranes showed an increased intermolecular motion in the transformed cell membranes. The temperature dependence of the (CH₂)_n line in the ¹H spectra in the temperature range 298–343 °K shows an activation energy for the lateral diffusion of the fluid phospholipid regions in the normal cell membranes while the transformed ones show practically no temperature dependence in this temperature range. The fluidity of the phospholipid region in the transformed cell membrane seems to be significantly higher than that observed in the normal cell material. These data support and extend the findings concerning the mobility of the concanavalin A binding/agglutinating sites on the surface of normal and virus-transformed cells and suggest further approaches to the study of the membrane alterations in tumor cells.     

Biomass Yield and Greenhouse Gas Emissions from a Drained Fen Peatland Cultivated with Reed Canary Grass under Different Harvest and Fertilizer Regimes

Reed canary grass (RCG, Phalaris arundinacea L.) is a suitable energy crop for cultivation in northern peatlands. However, the atmospheric impact of RCG cultivation as influenced by harvest frequency and fertilization is not clear. Here, we compared the biomass yield and greenhouse gas (GHG) balance for RCG cultivation in peatlands affected by cutting frequency and fertilizer managements. The managements included one-cut (OC) and two-cut (TC) systems that were either fertilized (TC-F) or unfertilized (TC-U) after the first cut in summer. Biomass yield of OC, TC-F and TC-U were 12, 16 and 11 Mg dry biomass per hectare per year, respectively. GHG fluxes of CO₂, N₂O and CH₄ were measured with closed chamber techniques in the period between first and second (final) harvest of the TC managements, i.e. from 15 June to 23 September 2011. In the GHG monitoring period of 100 days, all systems were net sources of CO₂ corresponding to 64?±?3, 217?±?15 and 50?±?23 g?CO₂-C?m^?2 (mean?±?standard error, n?=?3) from the OC, TC-F and TC-U systems, respectively. In the same period, emissions of N₂O from TC-F were ten times higher as compared to OC and TC-U. Emissions of CH₄ were negligible from all systems. The TC systems could not improve the GHG balance during cultivation (271, 663 and 210 g CO₂e-C?m^?2 emissions from the OC, TC-F and TC-U systems, respectively), but in a broader GHG life cycle perspective, the increased biomass yield by TC-F could replace more fossil fuel and offset at least some of the higher emissions from the system.     

Plant species from mesotrophic wetlands cause relatively high methane emissions from peat soil

Plants can influence methane emissions from wetland ecosystems by altering its production, consumption and transport in the soil. The aim of this study was to investigate how eight vascular plant species from mesotrophic to eutrophic wetlands vary in their influence on CH₄ emissions from peat cores, under low and high N supply. Additionally, we measured the production of low-molecular-weight organic acids (LOA) by the same species (also at low and high N supply), because LOA form a substrate for methanogenesis. There were considerable differences among species in their effects upon rates of CH₄ emission. Six of the species (Eriophorum latifolium Hoppe, Potentilla palustris (L.) Scop., Anthoxanthum odoratum (L.) s. str., Carex rostrata Stokes, Carex elata All., Carex acutiformis Ehrh.) increased CH₄ emissions up to five times compared to control peat cores without plants, whereas two species (Phalaris arundinacea L., Phragmites australis (Cav.) Trin. ex Steud.) had no effect. There was a weak negative correlation between plant biomass and CH₄ emission. N addition had no significant general effect upon CH₄ emission. LOA production varied considerably among species, and tended to be highest for species from mesotrophic habitats. LOA production was stimulated by N addition. We conclude that some species from mesotrophic wetlands tend to cause higher CH₄ emissions than species from eutrophic wetlands. This pattern, which contradicts what is often mentioned in literature, may be explained by the higher LOA production rates of species adapted to less productive habitats.     

Using Common Boundaries to Assess Methane Emissions: A Life Cycle Evaluation of Natural Gas and Coal Power Systems

There is consensus on the importance of upstream methane (CH₄) emissions to the life cycle greenhouse gas (GHG) footprint of natural gas systems, but inconsistencies among recent studies explain why some researchers calculate a CH₄ emission rate of less than 1% whereas others calculate a CH₄ emission rate as high as 10%. These inconsistencies arise from differences in data collection methods, data collection time frames, and system boundaries. This analysis focuses on system boundary inconsistencies. Our results show that the calculated CH₄ emission rate can increase nearly fourfold not by changing the magnitude of any particular emission source, but by merely changing the portions of the supply chain that are included within the system boundary. Our calculated CH₄ emission rate for extraction through pipeline transmission is 1.2% for current practices. Our model allows us to identify GHG contributors in the upstream supply chain, but also allows us to tie upstream findings to complete life cycle scenarios. If applied to the life cycles of power systems and assessed in terms of cumulative radiative forcing, the upstream CH₄ emission rate can be as high as 3.2% before the GHG impacts from natural gas power exceed those from coal power at any point during a 100‐year time frame.     

Effects of Winter Cover Crops Straws Incorporation on CH4 and N2O Emission from Double-Cropping Paddy Fields in Southern China

Residue management in cropping systems is believed to improve soil quality. However, the effects of residue management on methane (CH₄) and nitrous oxide (N₂O) emissions from paddy field in Southern China have not been well researched. The emissions of CH₄ and N₂O were investigated in double cropping rice (Oryza sativa L.) systems with straw returning of different winter cover crops by using the static chamber-gas chromatography technique. A randomized block experiment with three replications was established in 2004 in Hunan Province, China, including rice–rice–ryegrass (Lolium multiflorum L.) (Ry-R-R), rice–rice–Chinese milk vetch (Astragalus sinicus L.) (Mv-R-R) and rice–rice with winter fallow (Fa-R-R). The results showed that straw returning of winter crops significantly increased the CH₄ emission during both rice growing seasons when compared with Fa-R-R. Ry-R-R plots had the largest CH₄ emissions during the early rice growing season with 14.235 and 15.906 g m⁻² in 2012 and 2013, respectively, when Ry-R-R plots had the largest CH₄ emission during the later rice growing season with 35.673 and 38.606 g m⁻² in 2012 and 2013, respectively. The Ry-R-R and Mv-R-R also had larger N₂O emissions than Fa-R-R in both rice seasons. When compared to Fa-R-R, total N₂O emissions in the early rice growing season were increased by 0.05 g m⁻² in Ry-R-R and 0.063 g m⁻² in Mv-R-R in 2012, and by 0.058 g m⁻² in Ry-R-R and 0.068 g m⁻² in Mv-R-R in 2013, respectively. Similar result were obtained in the late rice growing season, and the total N₂O emissions were increased by 0.104 g m⁻² in Ry-R-R and 0.073 g m⁻² in Mv-R-R in 2012, and by 0.108 g m⁻² in Ry-R-R and 0.076 g m⁻² in Mv-R-R in 2013, respectively. The global warming potentials (GWPs) from paddy fields were ranked as Ry-R-R>Mv-R-R>Fa-R-R. As a result, straw returning of winter cover crops has significant effects on increase of CH₄ and N₂O emission from paddy field in double cropping rice system.     

[FeFe]-Hydrogenase models assembled into vesicular structures

Compartmentalization is a major prerequisite for the origin of life on earth according to Wächtershäuser “Iron-Sulfur-World”. The hypothesis is mainly based on an autocatalytic inorganic energy reproducing redox system consisting of iron and sulfur as requirement for the subsequent synthesis of complex organic structures. Here, we modified [FeFe]-hydrogenase models by means of covalent coupling to either oleic acid or the amphiphilic block copolymer polybutadiene-polyethyleneoxide (PB-PEO) and incorporated those into the membranes of vesicles composed of phospholipids (liposomes) or the unmodified amphiphilic polymer (polymersomes). We employed a [2Fe-2S] cluster as a hydrogenase model, since these structures are known to be suitable catalysts for the generation of H₂ in the presence of weak acids. Successful incorporation was confirmed by spectrophotometric iron quantification and the vesicles formed were characterized by size determination (photon correlation spectroscopy (PCS)), and zeta potential as well as by cryo-transmission electron microscopy (Cryo-TEM). The modified models could be incorporated into liposomes or polymersomes up to molar proportions of 3.15% and 28%, respectively. Due to the immobilization in vesicular bilayers the [FeFe]-hydrogenase models can even exhibit catalytic action under the particular conditions of the intravesicular microenvironment. Our results suggest that the vesicular systems described may be applied as a nanoreactor for the reduction of encapsulated substances by generating hydrogen and thus as a minimal cell model.     

Microbial Ecophysiology of Whey Biomethanation: Intermediary Metabolism of Lactose Degradation in Continuous Culture

The intermediary carbon and electron flow routes for lactose degradation during whey biomethanation were studied in continuous culture. The chemostat was operated under lactose-limited conditions with a 100-h retention time. The carbon balance observed for lactose degradation was 4.65 mmol of CH₄, 4.36 mmol of CO₂ and 1.15 mmol of cellular carbon per mmol of lactose consumed, with other intermediary metabolites (i.e., acetate, lactate, etc.) accounting for less than 2% of the lactose consumed. The carbon and electron recoveries for this biomethanation were 87 and 90%, respectively. ¹⁴C tracer studies demonstrated that lactose biomethanation occurred in three distinct but simultaneous phases. Lactose was metabolized primarily into lactate, ethanol, acetate, formate, and carbon dioxide. During this hydrolytic phase, 82% of the lactose was transformed into lactate. These metabolites were transformed into acetate and H₂-CO₂ in a second, acetogenic, phase. Finally, the direct methane precursors were transformed during the methanogenic phase, with acetate accounting for 81% of the methane formed. A general scheme is proposed for the exact carbon and electron flow route during lactose biomethanation, which predicts the prevalent microbial populations in this ecosystem.     

Vegetation controls methane emissions in a coastal brackish fen

Climate change and associated sea level rise will likely affect coastal ecosystems and lead to more frequent inundations. Plants are an important control for methane (CH₄) emissions in peatlands because the metabolism of the living plant can either enhance or attenuate CH₄ emissions and plant litter supplies an easily available carbon source for methanogenesis. Here we compare the contribution of various dominant plant species to methane emissions in a degraded, rewetted coastal brackish fen at the southern Baltic Sea coast in Northeast Germany. We analyse one year of bi-weekly static closed chamber data gathered at measurement spots that were located in different mono-dominant vegetation stands (Bolboschoenus maritimus (L.) Palla, Schoenoplectus tabernaemontani (C.C.Gmel.) Palla, Carex acutiformis Ehrh.). Furthermore, data on water level, water temperature, conductivity (sulphate), and several peat characteristics were recorded. Generally, the annual methane emissions were low with an average across vegetation stands of 14 kg CH₄ ha^?1 a^?1, which we related to high decomposition of peat after drainage and to relatively low water levels in summer. Nevertheless, methane emissions varied between different vegetation types with significantly higher methane fluxes (31.8 ± 5.7 kg CH₄ ha^?1 a^?1) from Bolboschoenus maritimus stands compared to Carex acutiformis and Schoenoplectus tabernaemontani stands (4.3 ± 1.2 and 5.7 ± 2.4 kg CH₄ ha^?1 a^?1, respectively). None of the environmental variables that have been recorded can explain this difference. Thus, vegetation composition seems to be an important driver for methane emissions in coastal brackish fens and may therefore be crucial with regard to recreation measures.     

张掖湿地甲烷通量动态特征及其影响因子

于2012年7月—2014年6月对地处干旱区的张掖湿地甲烷(CH_4)通量进行观测,分析其CH_4通量的变化特征及其影响因子。结果表明:CH_4通量的日变化趋势总体表现为白天大于夜间;不同季节CH_4通量排放特征差异明显,夏季最大,春秋次之,冬季最小;CH_4通量日总量与空气温度、土壤温度之间指数相关关系显著,其中4 cm处土壤温度与之相关性最强;1—6月摩擦风速(U*)与CH_4通量显著正相关;结合CO_2通量观测数据,研究时段张掖湿地净碳吸收量为495.92 g C m~(-2)a~(-1),为明显碳汇。     

The interaction of calcium and procaine with hepatocyte and hepatoma tissue culture cell plasma membranes studied by fluorescence spectroscopy

The fluorescent probe l-anilinonaphthalene-8-sulfonate (ANS) has been used to investigate the properties of plasma membranes derived from normal hepatocytes and from hepatoma tissue culture (HTC) cells as well as used to study the effects of Ca²⁺ and procaine on these membrane systems. The interaction of ANS with hepatocyte plasma membranes (50 nmol/mg protein; K_D = 120,μM) resulted in a marked enhancement of fluorescence and a 20-nm blue shift. Both Ca²⁺ and procaine further increased the fluorescence intensity. Binding studies showed no alteration in the number of ANS binding sites but a significant decrease in K_D (40–50 μm). Procaine was also shown to completely displace Ca²⁺ from the membrane. The interaction of ANS with HTC cell plasma membranes again resulted in an enhancement in fluorescence intensity but with different binding properties (102 nmol/mg protein; K_D = 74 μM) from the hepatocyte system. The addition of Ca⁺² resulted in the formation of high and low affinity ANS binding sites as shown by Scatchard plot analysis with K_D values of 15 μm and 50 μm. The effect of procaine on ANS fluorescence in the normal and transformed cell membranes was indistinguishable; however, in the latter system procaine only displaced 60% of the bound Ca²⁺. These studies suggest several structural and binding alterations between plasma membranes derived from hepatocytes and HTC cells.     

The mechanistic aspects of iron(III) porphyrin catalyzed oxidation reactions in mixed solvents

In the iron(III) porphyrin catalyzed oxidation reactions, the formation of various reactive intermediates have been observed to depend upon the nature of the catalyst, the oxidant and the solvent used for the study. The various iron(III) porphyrin catalysts such as F₂₀TPPFeCl, F₁₆TPPFeCl, F₁₂TPPFeCl and F₈TPPFeCl have been used in the present study to understand the effect of solvent system in the activation of the catalysts. As the terminal oxidant t-BuOOH has been used. It has been observed that acetonitrile contaminated with water activates all the catalysts. It has been noted that ∼9% of water in acetonitrile is the best solvent system for the activation of all the catalysts. The results obtained have been applied to successfully oxidize cyclohexene and cyclohexane by these oxidizing systems. It has also been observed that CH₃OH mixed with CH₂Cl₂ play a very important role in the activation of catalyst in hydroperoxide oxidizing system. The 33 ± 3% ratio of CH₃OH in CH₂Cl₂ acts as the most suitable solvent system to convert organopalladium compound 1a-c to 2a-c.     

Separation of respiratory reactions in Rhodospirillum rubrum: Inhibition studies with 2-hydroxydiphenyl

1. Respiration of chemotrophically and phototrophically grown Rhodospirillum rubrum is inhibited by 2-hydroxydiphenyl.2. Membrane-bound NADH oxidase and NADH: cytochrome c reductase are inhibited also. The inhibitor constant for both reactions (K_i) is 0.075±0.012 mM. NADH dehydrogenase is not inhibited significantly.3. The inhibition of succinate:cytochrome c reductase is associated for chemotrophic membranes with K_i = 0.22±0.03 mM and for phototrophic membranes with K_i = 0.49±0.09 mM. Succinate dehydrogenase is not affected by 2-hydroxydiphenyl.4. Cytochrome oxidase is inhibited only slightly.5. While NADH-dependent reactions in both phototrophic and chemotrophic membranes are inhibited maximally more than 95%, succinate-dependent reactions can be inhibited more than 95% only in chemotrophic membranes. In photo-trophic membranes the maximum inhibition of succinate-dependent reactions is about 70%.6. The type of inhibition in both cases 2 and 3 is non-competitive.7. While the reduction of b-type cytochrome is inhibited by 2-hydroxydiphenyl, the degree of ubiquinone reduction is not influenced. The data suggest that the site of inhibition is localized between ubiquinone and cytochrome b.8. Implications of these data for the respiratory electron transport system in R. rubrum are discussed.     

Mechanistic informations from trans-effect in the anation reactions of some bis(dimethylglyoximato)Rh(III) complexes

The parallel lability trend for the anation reactions of RRh(DH)₂H₂O (RCH₃, CH₃CH₂, CF₃CH₂, ClCH₂) and RCo(DH)₂H₂O complexes suggests a dissociative activation process for the reactions of the organorhodoximes. The high lability of these complexes, arising from the stabilization of the transition state, is not entirely due to the trans-effect of the R group, but, at least partially, to the labilizing effect of the equatorial macrocycle.     

Individual variation and repeatability of methane production from dairy cows estimated by the CO2 method in automatic milking system

The objectives of this study were to investigate the individual variation, repeatability and correlation of methane (CH₄) production from dairy cows measured during 2 different years. A total of 21 dairy cows with an average BW of 619±14.2 kg and average milk production of 29.1±6.5 kg/day (mean±s.d.) were used in the 1^st year. During the 2^nd year, the same cows were used with an average BW of 640±8.0 kg and average milk production of 33.4±6.0 kg/day (mean±s.d.). The cows were housed in a loose housing system fitted with an automatic milking system (AMS). A total mixed ration was fed to the cows ad libitum in both years. In addition, they were offered concentrate in the AMS based on their daily milk yield. The CH₄ and CO₂ production levels of the cows were analysed using a Gasmet DX-4030. The estimated dry matter intake (EDMI) was 19.8±0.96 and 23.1±0.78 (mean±s.d.), and the energy-corrected milk (ECM) production was 30.8±8.03 and 33.7±5.25 kg/day (mean±s.d.) during the 1^st and 2^nd year, respectively. The EDMI and ECM had a significant influence (P<0.001) on the CH₄ (l/day) yield during both years. The daily CH₄ (l/day) production was significantly higher (P<0.05) during the 2^nd year compared with the 1^st year. The EDMI (described by the ECM) appeared to be the key factor in the variation of CH₄ release. A correlation (r=0.54) of CH₄ production was observed between the years. The CH₄ (l/day) production was strongly correlated (r=0.70) between the 2 years with an adjusted ECM production (30 kg/day). The diurnal variation of CH₄ (l/h) production showed significantly lower (P<0.05) emission during the night (0000 to 0800 h). The between-cows variation of CH₄ (l/day, l/kg EDMI and l/kg ECM) was lower compared with the within-cow variation for the 1^st and 2^nd years. The repeatability of CH₄ production (l/day) was 0.51 between 2 years. In conclusion, a higher EDMI (kg/day) followed by a higher ECM (kg/day) showed a higher CH₄ production (l/day) in the 2^nd year. The variations of CH₄ (l/day) among the cows were lower than the within-cow variations. The CH₄ (l/day) production was highly repeatable and, with an adjusted ECM production, was correlated between the years.     

ω-3 polyunsaturated fatty acids and the cardiovascular system

ω-3 polyunsaturated fatty acids (PUFAs) (alpha-linolenic, eicosapentaenoic, and decosahexaenoic acids) are classified with essential fatty acids and are structural components of the phospholipid bilayer of cell membranes. ω-3 PUFAs incorporated into the phospholipid domain of cell membranes are metabolized to prostaglandins and thromboxanes (PGI ₃, PGE ₃, TxA, etc.), which significantly differ in biological activity from those formed in the arachidonic acid cascade (PGI ₂, PGE ₂, TxA ₂, etc.) and to which the antiaggregatory, antiatherogenic, and vasodilating effects of ω-3 PUFAs can largely be attributed. In addition, ω-3 PUFAs incorporated into cardiomyocyte cell membranes considerably modify the functional activity of transmembrane voltage-gated ion channels by causing a dose-dependent inhibition of the outward transmembrane sodium current, slowing down the work of transmembrane voltage-gated slow L-type calcium channels, and partially blocking the efflux of potassium ions from cardiomyocytes, thus showing the properties of class I, III, and IV antiarrhythmic drugs according to the Vaughnan Williams classification. Several clinical trials have supported experimental data that ω-3 PUFAs have membrane-stabilizing (antiarrhythmogenic) effects. For example, in the GISSI-Prevenzione trial, a large-scale, randomized, placebo-controlled study conducted in more than 9.5 thousand patients with left ventricular systolic dysfunction after myocardial infarction, ω-3 PUFA regular consumption significantly reduced the risk of sudden cardiac death by more than 50% in these patients. In our review, the mechanisms underlying the membrane-stabilizing, antiaggregatory, antiatherogenic, and vasodilating effects of ω-3 PUFAs and the clinical effectiveness of ω-3 PUFAs have been analyzed in terms of evidencebased pharmacology.     

The effect of some oligo-amines and -guanidines on membrane permeability in higher plants

The effect of a series of oligo-amines and -guanidines on the membranes of higher plants has been tested by measuring the efflux of betacyanin from beet root discs, and the loss of total ions from beet root and swede discs, beet and spinach leaf discs and apple cells in suspension culture. All of the naturally occurring di- and polyamines tested showed relatively little toxicity. Betacyanin efflux from beet root discs was reduced by diamines [NH₂(CH₂)_xNH₂] up to x = 10 or less. Ion efflux was minimal at x = 7. Within the triamine series [NH₂(CH₂)_xNH(CH₂)₃NH₂] for x = 8 or less, betacyanin efflux was reduced or unaffected, although total ion loss was increased by the triamines when x = 4 or more and especially by the longer chain amines (to x = 10). Similar behaviour was found in the tetra-amine series [NH₂(CH₂)₃NH(CH₂)_xNH(CH₂)₃NH₂] with betacyanin efflux reduced for x = 2–4 (spermine). Although spermine potentiated the toxicity effects of Guazatine {[NH₂C(NH)NH(CH₂)₈]₂NH} and Dodine [NH₂C(NH)NH(CH₂)₁₁,Me] in beet root discs, spermine and calcium ions reduced the ion efflux caused by these toxic guanidines and also by Synthalin B [NH₂C(NH)NH(CH₂)₁₂NHC(NH)NH₂] in swede discs, spinach leaves and apple cells. No significant reversal of ion loss was detected with putrescine, cadaverine or spermidine in swede discs. In the homologous series of monoguanidines [NH₂C(NH)NH(CH₂)_x?1Me] for x up to 18, greatest toxicity was shown for x = 10 and 11 in both betacyanin loss and total ion efflux in beet root discs. Greatest ion efflux from the apple cell suspension was found with x = 11 and 12. In the homologous series of diguanidines [NH₂C(NH)NH(CH₂),NHC(NH)NH₂] for x = 2–12 greatest toxicity was shown for x = 12 (the longest chain tested) in beet root and in the efflux of ions from apple cell suspension. Technical Guazatine was considerably more phytotoxic than pure Guazatine in all systems tested. p-Chloromercuribenzoate (p-CMB) potentiates the loss of betacyanin and total ions caused by Guazatine, Synthalin B, and Dodine in beet root discs. This effect of p-CMB is reversed by subsequent incubation in cysteine or mercaptoethanol, prior to treatment with the guanidines.     

Emissions of CH4 and N2O under Different Tillage Systems from Double-Cropped Paddy Fields in Southern China

Understanding greenhouse gases (GHG) emissions is becoming increasingly important with the climate change. Most previous studies have focused on the assessment of soil organic carbon (SOC) sequestration potential and GHG emissions from agriculture. However, specific experiments assessing tillage impacts on GHG emission from double-cropped paddy fields in Southern China are relatively scarce. Therefore, the objective of this study was to assess the effects of tillage systems on methane (CH₄) and nitrous oxide (N₂O) emission in a double rice (Oryza sativa L.) cropping system. The experiment was established in 2005 in Hunan Province, China. Three tillage treatments were laid out in a randomized complete block design: conventional tillage (CT), rotary tillage (RT) and no-till (NT). Fluxes of CH₄ from different tillage treatments followed a similar trend during the two years, with a single peak emission for the early rice season and a double peak emission for the late rice season. Compared with other treatments, NT significantly reduced CH₄ emission among the rice growing seasons (P<0.05). However, much higher variations in N₂O emission were observed across the rice growing seasons due to the vulnerability of N₂O to external influences. The amount of CH₄ emission in paddy fields was much higher relative to N₂O emission. Conversion of CT to NT significantly reduced the cumulative CH₄ emission for both rice seasons compared with other treatments (P<0.05). The mean value of global warming potentials (GWPs) of CH₄ and N₂O emissions over 100 years was in the order of NT<RT<CT, which indicated NT was significantly lower than both CT and RT (P<0.05). This suggests that adoption of NT would be beneficial for GHG mitigation and could be a good option for carbon-smart agriculture in double rice cropped regions.     

Influence of plant species and wastewater strength on constructed wetland methane emissions and associated microbial populations

Wastewater and treatment processes have been regarded as large contributions to sources of methane (CH₄). The flux rate of CH₄ in constructed wetlands (CWs) was evaluated to test the influence of plant species. Methane emission data showed large temporal and spatial variation ranging from 0 to 16.76 g CH₄ m⁻² day⁻¹. The highest CH₄ flux rate was obtained in the Zizania latifolia systems and higher emission was found with higher influent load. The methanogenic and methanotrophic microbial populations were studied to clarify the mechanisms of CH₄ emission. FISH analysis showed highest amounts of methanogens and methanotrophs in the Z. latifolia and Tytha latifolia systems. Linear regression between CH₄ emission and environmental parameters showed that the regression lines were not forced to pass through the origin, and the slopes of the lines of different systems were allowed to vary between vegetation cover.     

Effect of molecular weight of condensed tannins from warm-season perennial legumes on ruminal methane production in vitro

The objectives of the present study were to determine if the molecular weight of condensed tannins (CT) from warm-season perennial legumes affects the biological activity of CT relative to suppression of methane (CH₄) production by ruminants, and to identify potential North American native forage plants to use for mitigation of enteric CH₄ emission. Eight North American native warm-season perennial legumes were evaluated: Leucaena retusa Benth. (littleleaf leadtree), Desmanthus illinoensis (Michx.) MacMill. Ex B.L. Rob. & Fernald (Illinois bundleflower), Lespedeza stuevei Nutt. (tall lespedeza), Mimosa strigillosa Torr. & A. Gray (powderpuff), Neptunia lutea (Leavenworth) Benth. (yellow puff), two ecotypes of Acacia angustissima var. hirta (Nutt.) B.L. Rob (prairie acacia), and Desmodium paniculatum (L.) DC. var. paniculatum (panicledleaf ticktrefoil). Two introduced legumes were also included: Arachis glabrata Benth. (rhizoma peanut) and Lespedeza cuneata (Dum. Cours.) G. Don (sericea lespedeza). Forages were fermented with cattle rumen fluid for 48 h anaerobically using an in vitro gas production technique. D. paniculatum, L. stuevei, and M. strigillosa were high in CT, ranging from 11.7 to 12.5%. D. illinoensis, L. cuneata, N. lutea, and two ecotypes of A. angustissima var. hirta had less CT (P < 0.05), ranging from 8.1 to 8.9%, whereas L. retusa and A. glabrata had the least CT (P < 0.05), measuring 3.2 and 0.5%, respectively. Weight-average molecular weight (M_W) of CT ranged from 1483 Da for L. cuneata to 552 Da for L. stuevei. In vitro CH₄ production was greatest for L. retusa and A. glabrata at 40.7 mg/g DM and 38.2 mg/g DM, respectively. The least amount of in vitro CH₄ was produced by fermentation of two ecotypes of A. angustissima var. hirta, which measured 0.8 and 0.6 mg/g DM, respectively. In vitro CH₄ production regressed on CT M_W resulted in a R² of 0.0009 (P = 0.80), strongly suggesting that CT M_W does not explain the biological activity of in vitro CH₄ production by the forage legumes surveyed. Five of the seven North American native warm-season perennial legumes have promise for use in ruminant diets for the purpose of CH₄ emission mitigation.