Dependence of Wheat and Rice Respiration on Tissue Nitrogen and the Corresponding Net Carbon Fixation Efficiency Under Different Rates of Nitrogen Application

To quantitatively address the role of tissue N in crop respiration under various agricultural practices, and to consequently evaluate the impact of synthetic fertilizer N application on biomass production and respiration, and hence net carbon fixation efficiency （Encf）, pot and field experiments were carried out for an annual rotation of a rice-wheat cropping system from 2001 to 2003. The treatments of the pot experiments included fertilizer N application, sowing date and planting density. Different rates of N application were tested in the field experiments. Static opaque chambers were used for sampling the gas. The respiration as CO2 emission was detected by a gas chromatograph. A successive biomass clipping method was employed to determine the crop autotrophic respiration coefficient （Ra）. Results from the pot experiments revealed a linear relationship between Ra and tissue N content as Ra = 4.74N-1.45 （R^2= 0.85, P 〈 0.001）. Measurements and calculations from the field experiments indicated that fertilizer N application promoted not only biomass production but also increased the respiration of crops. A further investigation showed that the increase of carbon loss in terms of respiration owing to fertilizer N application exceeded that of net carbon gain in terms of aboveground biomass when fertilizer N was applied over a certain rate. Consequently, the Encf declined as the N application rate increased.

Variations in silicate concentration affecting photosynthetic carbon fixation by spring phytoplankton assemblages in surface water of the Strait of Malacca

The Strait of Malacca （SoM）, the world＇s busiest sea-route, is increasingly polluted as the rapid develop- ment of world trades, affecting phytoplankton primary productivity therein. The variations of surface phy- toplankton biomass, size-structure and carbon fixation were investigated across the SoM during the spring period （May 4 to 9, 2011）. Chlorophyll a concentration increased from 0.12 ptg/L at the northwest entrance of the SoM to a maximal 0.63 #g/L at narrowest section, and decreased to 0.10/.tg/L at the southeast entrance. Photosynthetic carbon fixation by phytoplankton coincided well with Chl a biomass, and increased from 10.8 to 22.3 pg C/（L.d）, then decreased to 9.21/zg C/（L.d）; while the carbon fixation rate showed an inverse pattern to the changes of Chl a, and decreased from 87.1 to 35.5 #g C/（#g Chl a.d） and increased thereafter to 95.3 btg C/（/2g Chl a.d）. Picophytoplankton cells （〈3/2m） contributed to more than 60% and 50% of the total Chl a and carbon fixation at both the entry waters; while the contributions of pico-cells decreased sharply to the minimum of 18.3% and 27.5% at the narrowest part of the SoM. In particular, our results showed that the silicate concentration positively regulated Chl a biomass and carbon fixation, reflecting that the higher silicate favoured the growth of phytoplankton and thus led to higher primary production in this strait.

NEW CATALYTIC SYSTEMS FOR THE FIXATION OF CO_2 Ⅲ.INFLUENCE OF ADDITIVES AND REACTION MEDIUM ON THE COPOLYMERIZATION OF CARBON DIOXIDE-EPICHLOROHYDRIN IN THE PRESENCE OF Nd (P_(204))_3-Al(i-Bu)_3

Copolymerization of carbon dioxide with epichlorohydrin was successfully carried out by usingNd(P_(204))_3-Al(i-Bu)_3 as catalyst (P_(204))=(RO)_2 POO--,R=CH_3 (CH_2),CH(C_2H_5) CH_2--). Addi-tion of carbonyl compounds into the catalyst decreased the carbon dioxide content of the copoly-mer to some extent. Compared to nonpolar solvents, ethereal and moderate polar solvents werefavourable to obtaining higher carbon dioxide content copolymer. The coincidence of these resultswith the assumed copolymerization scheme clearly indicated that the copolymerization proceeds via coordinate anionic mechanism.

Effects of Plastic Film Mulching on Soil Carbon Fixation Capacity and Fertility Level in Eastern Qinghai

[Objectives]To explore the effects of single application of chemical fertilizers on soil carbon fixation capacity and soil fertility under plastic film mulching conditions in eastern Qinghai,and to provide a theoretical basis for realizing the sustainable development of film mulching planting method in this area.[Methods]The effects of single application of chemical fertilizer cultivation mode under film mulching conditions on the soil organic carbon(SOC),labile organic carbon(LOC),carbon management index(CMI),extractable humus carbon(CHE),humic acid carbon(CHA),and fulvic acid carbon(CFA)in the cultivated layer(0-20 cm)were studied through three consecutive years of field experiments on dryland maize farmland in the eastern Qinghai.[Results]Under the film mulching condition,the SOC,LOC and CMI of the single application of chemical fertilizer cultivation mode were lower than that of the open field control.CHE,CHA and CFA increased with the increase of planting years,but the degree of increase was generally less than that of the open field control.With the increase of planting years,by 2020,the soil LOC/SOC value of film mulching decreased by 4.97%compared with before the start of the experiment,while the open field control increased by 1.11%;the organic carbon oxidation stability coefficient(KOS)of the film mulching was higher than that of the open field control;the soil CHA/CFA value and PQ value were higher than that of the open field control.[Conclusions]Under the condition of single application of chemical fertilizers,the continuous film mulching cultivation mode reduces the soil carbon fixation capacity,and soil organic carbon tends to be stable,which is not conducive to biological utilization and could reduce the soil fertility and degrade the soil quality,causing adverse effects on the stability of crop yield and sustainable production in the long run.

Stable Isotope Studies of Crop Carbon and Water Relations:A Review

Crop carbon and water relations research is important in the studies of water saving agriculture, breeding program, and energy and material cycles in soil plant atmosphere continuum （SPAC）. The purpose of this paper is to review the current state of knowledge on stable isotopes of carbon, oxygen, and hydrogen in the research of crop carbon and water relations, such as carbon isotope discrimination （△^13C） during carbon fixation process by photosynthesis, application of △^13C in crop water use efficiency （WUE） and breeding programs, oxygen isotope enrichment during leaf water transpiration, CO2 fixation by photosynthesis and release by respiration, application of hydrogen isotope composition （619） and oxygen isotope composition （6180） for determination of water source used by a crop, stable isotope coupling Keeling plot for investigating the carbon and water flux in ecosystem, energy and material cycle in SPAC and correlative integrative models on stable isotope. These aspects contain most of the stable isotope researches on crop carbon and water relations which have been widely explored internationally while less referred in China. Based on the reviewed literatures, some needs for future research are suggested.

In situ cultivation of deep-sea water with bicarbonate fueled a different microbial community

Some deep-sea microbes may incorporate inorganic carbon to reduce CO_(2) emission to upper layer and atmosphere.How the microbial inhabitants can be affected under addition of bicarbonate has not been studied using in situ fixed and lysed samples.In this study,we cultivated 40 L natural bottom water at~1000 m depth with a final concentration of 0.1 mmol/L bicarbonate for 40 min and applied multiple in situ nucleic acids collection(MISNAC)apparatus for nucleic acids extraction from the cultivation.Our classification result of the cultivation sample showed a distinct microbial community structure,compared with the samples obtained by Niskin bottle and six working units of MISNAC.Except for notable enrichment of Alteromonas,we detected prevalence of Asprobacter,Ilumatobacter and Saccharimonadales in the cultivation.Deep-sea lineages of Euryarchaeota,SAR406,SAR202 and SAR324 were almost completely absent from the cultivation and Niskin samples.This study revealed the dominant microbes affected by bicarbonate addition and Niskin sampling,which suggested rapid responses of deep-sea microbes to the environmental changes.

Effects of Fertilization Type on Carbon Storage of Soil and Crops in Mine Wasteland

Taking a three-year fertilization trial in mine reclamation soil from Shanxi Province, China as an example, the effects of different fertilization treatments on soil carbon storage and carbon fixation by corn were studied in this paper. Four treatments were designed in the experiment, including fertilizer （ F）, organic manure （ M）, half organic manure plus half fertilizer （ FM） and control （CK）. The results showed that fertilization had certain roles in increasing organic carbon storage of mine reclamation soil, and the application of single or combined organic and inorganic fertilizers had the most remarkable influence. Meanwhile, the treatment of single or combined organic and inorganic fertilizers could improve the carbon fixation capacity of corn prominently, and increased soil organic matter input. Thus, the application of organic manure or combined organic and inorganic fertilizer has great contribution to enhancing soil carbon sink and sustainable development of agriculture. However, the combined application of organic and inorganic fertilizer is the best choice for agricultural field based on economic consideration.

Importance of periphytic biofilms for carbon cycling in paddy fields:A review

Paddy fields play an important role in global carbon(C) cycling and are an important source of methane(CH_(4)) emissions. Insights into the processes influencing the dynamics of soil organic C(SOC) in paddy fields are essential for maintaining global soil C stocks and mitigating climate change. Periphytic biofilms composed of microalgae, bacteria, and other microorganisms are ubiquitous in paddy fields, where they directly mediate the transfer of elements at the soil-water interface. However, their contributions to C turnover and exchange have been largely neglected. Periphytic biofilms affect and participate in soil C dynamics by altering both abiotic(e.g., pH and redox potential) and biotic conditions(e.g., microbial community composition and metabolism). This review summarizes the contributions of periphytic biofilms to soil C cycling processes, including carbon dioxide fixation, SOC mineralization, and CH_(4) emissions. Future research should be focused on: i) the mechanisms underlying periphytic biofilm-induced C fixation and turnover and ii) quantifying the contributions of periphytic biofilms to soil C uptake, stabilization, and sequestration in paddy fields.

Decomposition and stabilization of organic matter in an old-growth tropical riparian forest:effects of soil properties and vegetation structure

Background:Nutrient cycling in tropical forests has a large importance for primary productivity,and decomposition of litterfall is a major process influencing nutrient balance in forest soils.Although large-scale factors strongly influence decomposition patterns,small-scale factors can have major influences,especially in old-growth forests that have high structural complexity and strong plant-soil correlations.Here we evaluated the effects of forest structure and soil properties on decomposition rates and stabilization of soil organic matter using the Tea Bag Index(TBI)in an old-growth riparian forest in southeastern Brazil.These data sets were described separately using Principal Components Analysis(PCA).The main axes for each analysis,together with soil physical properties(clay content and soil moisture),were used to construct structural equations models that evaluated the different parameters of the TBI,decomposition rates and stabilization factor.The best model was selected using Akaike’s criterion.Results:Forest structure and soil physical and chemical properties presented large variation among plots within the studied forest.Clay content was strongly correlated with soil moisture and the first PCA axis of soil chemical properties,and model selection indicated that clay content was a better predictor than this axis.Decomposition rates presented a large variation among tea bags(0.009 and 0.098 g·g^(−1)·d−1)and were positively related with forest structure,as characterized by higher basal area,tree density and larger trees.The stabilization factor varied between 0.211–0.426 and was related to forest stratification and soil clay content.Conclusions:The old-growth forest studied presented high heterogeneity in both forest structure and soil properties at small spatial scales,that influenced decomposition processes and probably contributed to small-scale variation in nutrient cycling.Decomposition rates were only influenced by forest structure,whereas the stabilization factor was influenced by both forest structure and soil properties.Heterogeneity in ecological processes can contribute to the resilience of old-growth forests,highlighting the importance of restoration strategies that consider the spatial variation of ecosystem processes.

Polystyrene-supported Phenol/DMAP： an Efficient Binary Catalyst System for CO2 Fixation to Give Cyclic Carbonates

Polystyrene-supported phenol （PS-PhOH） was successfully synthesized by alkylation reaction of phenol with 2% DVB cross-linked chloromethylated polystyrene and characterized by IR spectra and elemental analysis. In conjunction with an organic base such as DMAP, DBU, triethylamine （Et3N）, diethylamine （Et2NH） or pyridine, the PS-PhOH could effectively catalyze the coupling reaction of carbon dioxide with epoxides to give cyclic carbonates in high yield and selectivity under mild conditions. The binary catalyst system of the PS-PhOH/DMAP was found to be the most active. The influence of reaction temperature, carbon dioxide pressure and reaction time on the yield of product was carefully investigated. The PS-PhOH could be recycled by simple filtration for at least up to ten times without loss of catalytic activity.

Detailed profiling of carbon fixation of in silico synthetic autotrophy with reductive tricarboxylic acid cycle and Calvin-Benson-Bassham cycle in Esherichia coli using hydrogen as an energy source

Carbon fixation is the main route of inorganic carbon in the form of CO2 into the biosphere.In nature,RuBisCO is the most abundant protein that photosynthetic organisms use to fix CO2 from the atmosphere through the Calvin-Benson-Bassham(CBB)cycle.However,the CBB cycle is limited by its low catalytic rate and low energy efficiency.In this work,we attempt to integrate the reductive tricarboxylic acid and CBB cycles in silico to further improve carbon fixation capacity.Key heterologous enzymes,mostly carboxylating enzymes,are inserted into the Esherichia coli core metabolic network to assimilate CO2 into biomass using hydrogen as energy source.Overall,such a strain shows enhanced growth yield with simultaneous running of dual carbon fixation cycles.Our key results include the following.(i)We identified two main growth states:carbon-limited and hydrogenlimited;(ii)we identified a hierarchy of carbon fixation usage when hydrogen supply is limited;and(iii)we identified the alternative sub-optimal growth mode while performing genetic perturbation.The results and modeling approach can guide bioengineering projects toward optimal production using such a strain as a microbial cell factory.

Carbon dioxide fixation by Chlorella sp.USTB-01 with a fermentor-helical combined photobioreactor

A promising microalgal strain isolated from fresh water,which can grow both autotrophically on inorganic carbon under lighting and heterotrophically on organic carbon without lighting,was identified as Chlorella sp.USTB-01 with the phylogenetic analysis based on 18S ribosomal ribonucleic acid(rRNA)gene sequences.In the heterotrophic batch culture,more than 20.0 g·L^(-1)of cell dry weight concentration(DWC)of Chlorella sp.USTB-01 was obtained at day 5,and which was used directly to seed the autotrophic culture.A novel fermentor-helical combined photobioreactor was established and used to cultivate Chlorella sp.USTB-01 for the fixation of carbon dioxide(CO_(2)).It showed that the autotrophic growth of Chlorella sp.USTB-01 in the combined photobioreactor was more effective than that in the fermentor alone and the maximum DWC of 2.5 g·L^(-1)was obtained at day 6.The highest CO_(2)fixation of 95%appeared on day 1 in the exponential growth phases of Chlorella sp.USTB-01 and 49.8%protein was found in the harvested microalgal cells.

Determination of carbon-fixing potential of Bathyarchaeota in marine sediment by DNA stable isotope probing analysis

Bathyarchaeota is believed to play a crucial role in the global carbon cycle due to its vast biomass,broad distribution,and diverse habitat.However,its physiological and metabolic features are hard to determine without pure culture.While metagenomic analyses have shown that Bathyarchaeota has a complete inorganic carbon fixation(Wood-Ljungdahl,WL)pathway,no direct functional confirmation has been reported.To explore the inorganic carbon fixation ability of Bathyarchaeota,we used lignin and sodium bicarbonate-^(13)C(NaH^(13)CO_(3))in the long-term incubation of marine sediment samples.We found that Bathyarchaeota grew continuously in the cultivation system with lignin,and its abundance increased up to 15.3 times after10 months,increasing its fraction of all archaea from 30%to 80%.We monitored theδ^(13)C of total organic carbon to identify microbial carbon fixation in the cultivation systems,finding that it increased in the first month while NaH^(13)CO_(3)was present but only increased continuously afterward when lignin was also present.Furthermore,ultracentrifugation was performed on DNA extracted from samples at different cultivation stages to separate DNA of different buoyant densities,and bathyarchaeotal and bacterial 16S ribosomal RNA(r RNA)gene abundance were quantified using qPCR.Compared to bacteria,bathyarchaeotal 16S rRNA tended to be concentrated in heavy layers after 4 months of incubation with lignin and NaH^(13)CO_(3),indicating that Bathyarchaeota DNA contained^(13)C through proliferation based on lignin utilization and NaH^(13)CO_(3)assimilation,proving the carbon fixation capacity of Bathyarchaeota.

Realizing Stable Carbonate Electrolytes in Li-O_(2)/CO_(2)Batteries

The increasing demand for high-energy storage systems has propelled the development of Li-air batteries and Li-O_(2)/CO_(2)batteries to elucidate the mechanism and extend battery life.However,the high charge voltage of Li2CO3 accelerates the decomposition of traditional sulfone and ether electrolytes,thus adopting high-voltage electrolytes in Li-O_(2)/CO_(2)batteries is vital to achieve a stable battery system.Herein,we adopt a commercial carbonate electrolyte to prove its excellent suitability in Li-O_(2)/CO_(2)batteries.The generated superoxide can be captured by CO_(2)to form less aggressive intermediates,stabilizing the carbonate electrolyte without reactive oxygen species induced decomposition.In addition,this electrolyte permits the Li metal plating/stripping with a significantly improved reversibility,enabling the possibility of using ultra-thin Li anode.Benefiting from the good rechargeability of Li2CO3,less cathode passivation,and stabilized Li anode in carbonate electrolyte,the Li-O_(2)/CO_(2)battery demonstrates a long cycling lifetime of 167 cycles at 0.1 mA·cm^(-2)and 0.25 mAh·cm^(-2).This work paves a new avenue for optimizing carbonate-based electrolytes for Li-O_(2)and Li-O_(2)/CO_(2)batteries.

Photosynthesis of Submerged and Surface Leaves of the Dwarf Water Lily(Nymphoides aquatica)Using PAM Fluorometry

Dwarf Water Lilies Nymphoides aquatica(J.F.Gmel)Kuntze have floating and submerged leaves.Some submerged aquatic vascular plants have a form of CAM(Crassulacean Acid Metabolism)called Submerged Aquatic Macrophyte(SAM)metabolism.Blue-diode based PAM technology was used to measure the Photosynthetic Oxygen Evolution Rate(POER:1O_(2)≡4e^(-)).Optimum Irradiance(E_(opt)),maximum POER(POER_(max))and quantum efficiency(α_(0))all vary on a diurnal cycle.The shape of the POER vs.E curves is different in seedling,submerged and surface leaves.Both E_(opt) and POER_(max) are very low in seedling leaves(E_(opt)≈104μmol photon m^(-2) s^(-1),PPFD;POER_(max)≈4.95µmol O_(2) g^(-1) Chl a s^(-1)),intermediate in mature submerged leaves(E_(opt)≈419µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈38.1µmol O_(2) g^(-1) Chl a s^(-1))and very high in surface leaves(E_(opt)≈923µmol photon m^(-2) s^(-1) PPFD,POER_(max)≈76.1µmol O_(2) g^(-1) Chl a s^(-1)).Leaf titratable acid(C4 acid pool)is too small(≈20 to 50 mol H+m^(-3))to support substantial SAM metabolism.Gross daily photosynthesis of surface leaves is≈3.71 g C m^(-2) d^(-1) in full sun and as much as 1.4 gC m^(-2) d^(-1) in shaded submerged leaves.There is midday inhibition of photosynthesis.

Recent Advances on Metal-Organic Frameworks in the Conversion of Carbon Dioxide

With the development of modern industry,global warming is becoming a challenging issue due to the emissions of large quantities of greenhouse gases,mainly carbon dioxide(CO_(2)).The conversion of CO_(2)to useful compounds is considered as an effective and economic way to solve such a climate problem.Metal-organic frameworks(MOFs)are an emerging class of porous crystalline materials that have shown great potential in the conversion of CO_(2).The advantages of MOFs in CO 2 conversion lie in their high surface areas,adjustable pore size,and high porosity.More importantly,desirable functional sites can be easily designed and precisely installed to the pore wall of target MOFs by pre-assembly and/or post-synthetic modification(PSM)ways.This review summarizes the recent advances in constructing MOF catalysts for the application in CO_(2)conversion.We believe that the design and synthesis of MOF catalysts for CO_(2)conversion can be a promising way to solve the“greenhouse effect”.

Iron and lead ion adsorption by microbial flocculants in synthetic wastewater and their related carbonate formation

Although microbial treatments of heavy metal ions in wastewater have been studied, the removal of these metals through incorporation into carbonate minerals has rarely been reported. To investigate the removal of Fe^3＋ and Pb^2＋, two representative metals in wastewater, through the precipitation of carbonate minerals by a microbial flocculant （MBF） produced by Bacillus mucilaginosus. MBF was added to synthetic wastewater containing different Fe^3＋ and Pb^2＋ concentrations, and the extent of flocculation was analyzed. CO2 was bubbled into the mixture of MBF and Fe^3＋/Pb^2＋ to initiate the reaction. The solid substrates were analyzed via X-ray diffraction, transmission electron microscopy and energy dispersive spectroscopy. The results showed that the removal efficiency decreased and the MBF adsorption capacity for metals increased with increasing heavy metal concentration. In the system containing MBF, metals （Fe^3＋ and Pb^2＋）, and CO2, the concentrated metals adsorbed onto the MBF combined with the dissolved CO2, resulting in oversaturation of metal carbonate minerals to form iron carbonate and lead carbonates. These results may be used in designing a method in which microbes can be utilized to combine CO2 with wastewater heavy metals to form carbonates, with the aim of mitigating environmental problems.

Synthetic biology for CO2 fixation

Recycling of carbon dioxide(CO_2) into fuels and chemicals is a potential approach to reduce CO_2 emission and fossil-fuel consumption. Autotrophic microbes can utilize energy from light, hydrogen, or sulfur to assimilate atmospheric CO_2 into organic compounds at ambient temperature and pressure. This provides a feasible way for biological production of fuels and chemicals from CO_2 under normal conditions. Recently great progress has been made in this research area, and dozens of CO_2-derived fuels and chemicals have been reported to be synthesized by autotrophic microbes. This is accompanied by investigations into natural CO_2-fixation pathways and the rapid development of new technologies in synthetic biology. This review first summarizes the six natural CO_2-fixation pathways reported to date, followed by an overview of recent progress in the design and engineering of CO_2-fixation pathways as well as energy supply patterns using the concept and tools of synthetic biology. Finally, we will discuss future prospects in biological fixation of CO_2.

DBU-Mediated Carboxylative Coupling of Primary Amines,Carbon Dioxide and Propargyl Chlorides

A carboxylative coupling reaction of various primary amine and 3-phenyl-2-propynyl or 2-nonynyl chloride in the presence of 8-diazabicyclo[5.4.0]undec-7-ene(DBU)using carbon dioxide as carboxylative reagent was presented.This transition-metal free reaction system shows broad substrate scope and gives a series of propargylcarbamates in moderate to good yield.The obtained N-alkyl substituted carbamate product can undergo base-catalyzed intramolecular cyclization reaction to afford functionalized 4-methylene-2-oxazolidinone in good yield.

Silver-Catalyzed Three-Component Coupling of Carbon Dioxide, Amines and α-Diazoesters

A silver-catalyzed three-component coupling reaction of carbon dioxide, amines and α-diazoesters has been developed for the first time. The novel reaction provides an efficient and practical methodology for the synthesis of a wide range of new α-carbamoyloxy esters, which are difficult to prepare by existing methods. The advantages of the method include the use of readily available starting materials, simple catalytic system, good atom economy and high functional group tolerance.