Characterization of Light-Enhanced Respiration in Cyanobacteria

In eukaryotic algae, respiratory O₂ uptake is enhanced after illumination, which is called light-enhanced respiration (LER). It is likely stimulated by an increase in respiratory substrates produced during photosynthetic CO₂ assimilation and function in keeping the metabolic and redox homeostasis in the light in eukaryotic cells, based on the interactions among the cytosol, chloroplasts, and mitochondria. Here, we first characterize LER in photosynthetic prokaryote cyanobacteria, in which respiration and photosynthesis share their metabolisms and electron transport chains in one cell. From the physiological analysis, the cyanobacterium Synechocystis sp. PCC 6803 performs LER, similar to eukaryotic algae, which shows a capacity comparable to the net photosynthetic O₂ evolution rate. Although the respiratory and photosynthetic electron transports share the interchain, LER was uncoupled from photosynthetic electron transport. Mutant analyses demonstrated that LER is motivated by the substrates directly provided by photosynthetic CO₂ assimilation, but not by glycogen. Further, the light-dependent activation of LER was observed even with exogenously added glucose, implying a regulatory mechanism for LER in addition to the substrate amounts. Finally, we discuss the physiological significance of the large capacity of LER in cyanobacteria and eukaryotic algae compared to those in plants that normally show less LER.     

Rational Design of Covalent Multiheme Cytochrome-Carbon Dot Biohybrids for Photoinduced Electron Transfer

Biohybrid systems can combine inorganic light-harvesting materials and whole-cell biocatalysts to utilize solar energy for the production of chemicals and fuels. Whole-cell biocatalysts have an intrinsic self-repair ability and are able to produce a wide variety of multicarbon chemicals in a sustainable way with metabolic engineering. Current whole-cell biohybrid systems have a yet undefined electron transfer pathway between the light-absorber and metabolic enzymes, limiting rational design. To enable engineering of efficient electron transfer pathways, covalent biohybrids consisting of graphitic nitrogen doped carbon dots (g-N-CDs) and the outer-membrane decaheme protein, MtrC from Shewanella oneidensis MR-1 are developed. MtrC is a subunit of the MtrCAB protein complex, which provides a direct conduit for bidirectional electron exchange across the bacterial outer membrane. The g-N-CDs are functionalized with a maleimide moiety by either carbodiimide chemistry or acyl chloride activation and coupled to a surface-exposed cysteine of a Y657C MtrC mutant. MtrC∼g-N-CD biohybrids are characterized by native and denaturing gel electrophoresis, chromatography, microscopy, and fluorescence lifetime spectroscopy. In the presence of a sacrificial electron donor, visible light irradiation of the MtrC∼g-N-CD biohybrids results in reduced MtrC. The biohybrids may find application in photoinduced transmembrane electron transfer in S. oneidensis MR-1 for chemical synthesis in the future.     

In Situ Photosynthesis of an MAPbI3/CoP Hybrid Heterojunction for Efficient Photocatalytic Hydrogen Evolution

Halide perovskite like methylammonium lead iodide perovskite (MAPbI₃) with its prominent optoelectronic properties has triggered substantial concerns in photocatalytic H₂ evolution. In this work, to attain preferable photocatalytic performance, a MAPbI₃/cobalt phosphide (CoP) hybrid heterojunction is constructed by a facile in situ photosynthesis approach. Systematic investigations reveal that the CoP nanoparticle can work as co‐catalyst to not only extract photogenerated electrons effectively from MAPbI₃ to improve the photoinduced charge separation, but also facilitate the interfacial catalytic reaction. As a result, the as‐achieved MAPbI₃/CoP hybrid displays a superior H₂ evolution rate of 785.9 µmol h^?1 g^?1 in hydroiodic acid solution within 3 h, which is ≈8.0 times higher than that of pristine MAPbI₃. Furthermore, the H₂ evolution rate of MAPbI₃/CoP hybrid can reach 2087.5 µmol h^?1 g^?1 when the photocatalytic reaction time reaches 27 h. This study employs a facile in situ photosynthesis strategy to deposit the metal phosphide co‐catalyst on halide perovskite nanocrystals to conduct photocatalytic H₂ evolution reaction, which may stimulate the intensive investigation of perovskite/co‐catalyst hybrid systems for future photocatalytic applications.     

基于作用光谱的西红花LED补光灯具光谱研究

西红花是一种经济价值很高的药材。光谱是植物生长的重要影响因素,因此探索最适合西红花物质积累的补光光谱很有意义,但目前还缺乏对西红花室外补光参数的研究。本文利用西红花叶片的作用光谱,半定量分析补光灯具对西红花物质积累的增益。进一步评估了不同光谱的LED补光灯具对西红花干物质的增益效用。理论计算结果表明,低色温的宽光谱白光或红光与少量蓝光的组合更适合作为西红花LED补光灯具的光谱。     

用振荡射流抑制蓝藻滋长防止泥沙淤积

按照控制论的"反馈—放大—振荡"原理所构建的双稳态流体自控振荡器,可交替地从其两个输出孔断续地喷射出变向的水射束,从而促使周围水体激烈紊动,加强水中物质的交换能力.振荡射流扰动后,蓝藻能获得的光合能量将降低4倍.由于悬浮功Ws相对于自变量体积含沙量Sv的二阶导数为负值,高含沙浓度的泥浆流不但不会淤积反而会急剧冲刷河床.流控振荡器激扰促紊会导致分层流失稳,从而增大河流输沙能力.     

NixSy Nanowalls/Nitrogen‐Doped Graphene Foam Is an Efficient Trifunctional Catalyst for Unassisted Artificial Photosynthesis

Solar‐to‐hydrogen (STH) conversion through unassisted artificial photosynthesis (APS) devices is one of the promising and environmentally friendly strategies for sustainable development. However, the practical large‐scale application of the unassisted APS devices is impeded by the need for expensive noble metal‐based catalysts in photovoltaics and/or electrolyzers. Herein, well‐aligned 2D Ni_xS_y nanowalls (2D Ni_xS_y NWs) on a 3D nitrogen‐doped graphene foam (3D NGF) are synthesized and further employed it in unassisted APS. Due to the positive synergistic effect between the highly electrocatalytic activity of Ni_xS_y NW and excellent conductivity of NGF, this low cost material of (2D/3D) Ni_xS_y NW/NGF is highly efficient as a multifunctional catalyst in various applications: a counterelectrode for dye‐sensitized solar cell (DSSC) and a “bifunctional” electrocatalyst for oxygen and hydrogen evolution for electrocatalytic overall water splitting. Furthermore, three Ni_xS_y NW/NGF‐based DSSCs as a tandem cell for unassisted solar‐driven overall water splitting is connected, using Ni_xS_y NW/NGF itself on nickel foams as the anode and cathode. Impressively, such integrated photovoltaic‐electrolyzer APS device can achieve an STH efficiency of 3.2% with an excellent stability and low cost. This work opens an avenue to advanced multifunctional materials for the low‐cost and unassisted solar‐driven overall water splitting.     

Carbon Nanotube–Graphitic Carbon Nitride Hybrid Films for Flavoenzyme‐Catalyzed Photoelectrochemical Cells

In green plants, solar‐powered electrons are transferred through sophistically arranged photosystems and are subsequently channelled into the Calvin cycle to generate chemical energy. Inspired by the natural photosynthetic scheme, a photoelectrochemical cell (PEC) is constructed configured with protonated graphitic carbon nitride (p‐g‐C₃N₄) and carbon nanotube hybrid (CNT/p‐g‐C₃N₄) film cathode, and FeOOH‐deposited bismuth vanadate (FeOOH/BiVO₄) photoanode for the production of industrially useful chiral alkanes using an old yellow enzyme homologue from Thermus scotoductus (TsOYE). In the biocatalytic PEC platform, photoexcited electrons provided by the FeOOH/BiVO₄ photoanode are transferred to the robust and self‐standing CNT/p‐g‐C₃N₄ hybrid film that electrocatalytically reduces flavin mononucleotide (FMN) mediator. The p‐g‐C₃N₄ promotes a two‐electron reduction of FMN coupled with an accelerated electron transfer by the conductive CNT network. The reduced FMN subsequently delivers the electrons to TsOYE for the highly enantioselective conversion of ketoisophorone to (R)‐levodione. Under light illumination (>420 nm) and external bias, (R)‐levodione is synthesized with the enantiomeric excess value of above 83%, not influenced by the scale of applied bias, simultaneously exhibiting stable and high current efficiency. The results suggest that the biocatalytic PEC made up of economical materials can selectively synthesize high‐value organic chemicals using water as an electron donor.     

MODIS enhanced vegetation index predicts tree species richness across forested ecoregions in the contiguous U.S.A.

With the expectation of major shifts in climate, ecologists have focused attention on developing predictive relationships between current climatic conditions and species diversity. Climatic relationships appear best defined at regional rather than local levels. In reference to tree diversity, process-based models that express gross primary production (GPP) as an integrated function of climate seem most appropriate. Since 2000, NASA's MODIS satellite has provided composite data at 16-day intervals to produce estimates of GPP that compare well with direct measurements. The MODIS enhanced vegetation index (EVI), which is independent of climatic drivers, also appears a good surrogate to estimate seasonal patterns in GPP. In this paper we identified 65 out of 84 delineated ecoregions distributed across the contiguous U.S.A., within which sufficient (≥ 200) Federal Inventory and Analysis survey plots were available to predict the total number of tree species, which varied from 17 to 164. Four different formulations of EVI were compared: The annual maximum, the annual integrated, the growing season defined mid-point and growing season averaged values. The growing season mid-point EVI defined the beginning and end of the active growing season. In all formulations of EVI, a polynomial function accounted for about 60% of the observed variation in tree diversity, with additional precision increasing to 80% when highly fragmented ecoregions with < 50% forest cover were excluded. Maps comparing predicted with measured tree richness values show similar patterns except in the Pacific Northwest region where a major extinction of tree genera is known to have occurred during the late Pliocene. The extent that these relationships remain stable under a changing climate can be evaluated by determining if the MODIS climate-driven estimate of GPP continues to match well with EVI patterns and systematic resurveys of forest vegetation indicate that tree species are able to adjust rapidly to climatic variation.     

不同粳稻品种产量构成因素与光合特性的研究

以36个水稻品种或品系为试材,研究了不同类型粳稻品种的产量构成因素、光合性状及其对产量的影响。结果表明,产量构成因素对产量的直接作用以有效穗为主。在齐穗期和灌浆期,紧穗型和半紧穗型品种的净光合速率相对较高。在齐穗期,半紧穗型品种细胞间CO2浓度较高;半紧穗型和紧穗型品种的蒸腾速率达到4mmol·m-2·s-1,散穗和半散穗型品种相对较低。半紧穗型品种在整个生育时期都具有较高的叶面积指数,成熟期叶绿素含量下降缓慢,抗衰老能力较强,产量较高。     

Satellite-based modeling of gross primary production in a seasonally moist tropical evergreen forest

A CO₂ eddy flux tower study has recently reported that an old-growth stand of seasonally moist tropical evergreen forest in Santarém, Brazil, maintained high gross primary production (GPP) during the dry seasons [Saleska, S. R., Miller, S. D., Matross, D. M., Goulden, M. L., Wofsy, S. C., da Rocha, H. R., de Camargo, P. B., Crill, P., Daube, B. C., de Freitas, H. C., Hutyra, L., Keller, M., Kirchhoff, V., Menton, M., Munger, J. W., Pyle, E. H., Rice, A. H., & Silva, H. (2003). Carbon in amazon forests: Unexpected seasonal fluxes and disturbance-induced losses. Science, 302, 1554-1557]. It was proposed that seasonally moist tropical evergreen forests have evolved two adaptive mechanisms in an environment with strong seasonal variations of light and water: deep roots system for access to water in deep soils and leaf phenology for access to light. Identifying tropical forests with these adaptive mechanisms could substantially improve our capacity of modeling the seasonal dynamics of carbon and water fluxes in the tropical zone. In this paper, we have analyzed multi-year satellite images from the VEGETATION (VGT) sensor onboard the SPOT-4 satellite (4/1998-12/2002) and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Terra satellite (2000-2003). We reported temporal analyses of vegetation indices and simulations of the satellite-based vegetation photosynthesis model (VPM). The Enhanced Vegetation Index (EVI) identified subtle changes in the seasonal dynamics of leaf phenology (leaf emergence, leaf aging and leaf fall) in the forest, as suggested by the leaf litterfall data. The land surface water index (LSWI) indicated that the forest experienced no water stress in the dry seasons of 1998-2002. The VPM model, which uses EVI, LSWI and site-specific climate data (air temperature and photosynthetically active radiation, PAR) for 2001-2002, predicted high GPP in the late dry seasons, consistent with observed high evapotranspiration and estimated GPP from the CO₂ eddy flux tower.