Issues and perspectives for investigating root responses to elevated atmospheric carbon dioxide

A thorough assessment of how plants and ecosystems will respond to increasing concentrations of atmospheric CO₂ requires that the responses of root systems and associated belowground processes be understood. Static measures of root-to-shoot ratio have not been satisfactory for describing the integrated responses of plants to CO₂-enriched atmospheres, but research with a process orientation has suggested that elevated CO₂ can stimulate root growth or root activity and provide a positive feedback on plant growth. There are, however, critical questions concerning the relevance of root data from short-term studies with potted plants when scaling to questions about plants in the field. Data on root responses to CO₂ enrichment in the field are fragmentary, but they allow us to more clearly define research questions for further investigation. Three perspectives for analyzing the significance of root responses as a component of the overall response of the terrestrial biosphere to increasing atmospheric CO₂ are suggested: (1) roots as a platform for nutrient acquisition and a mediator of whole-plant response to CO₂; (2) carbon storage in roots as a component of whole-plant carbon storage; and (3) effects of CO₂ enrichment on root turnover and the implications for carbon storage as soil organic matter. The relative importance of these different perspectives will vary depending on the ecosystem of interest and the larger-scale issues being considered.     

Emission scenario of non-CO2 gases from energy activities and other sources in China

This paper gives a quantitative analysis on the non-CO₂ emissions related to energy demand, energy activities and land use change of six scenarios with different development pattern in 2030 and 2050 based on IPAC emission model. The various mitigation technologies and policies are assessed to understand the corresponding non-CO₂ emission reduction effect. The research shows that the future non-CO₂ emissions of China will grow along with increasing energy demand, in which thermal power and transportation will be the major emission and mitigation sectors. During the cause of future social and economic development, the control and mitigation of non-CO₂ emissions is a problem as challenging and pressing as that of CO₂ emissions. This study indicates that the energy efficiency improvement, renewable energy, advanced nuclear power generation, fuel cell, coal-fired combined cycle, clean coal and motor vehicle emission control technologies will contribute to non-CO₂ emissions control and mitigation.

     

Phylogeny, classification and taxonomy of European dragonflies and damselflies (Odonata): a review

Although Europe is the cradle of dragonfly systematics and despite great progress in the last 2 decades, many issues in naming its species and understanding their evolutionary history remain unresolved. Given the public interest, conservation importance and scientific relevance of Odonata, it is time that remaining questions on the species?? status, names and affinities are settled. We review the extensive but fragmentary literature on the phylogeny, classification and taxonomy of European Odonata, providing summary phylogenies for well-studied groups and an ecological, biogeographic and evolutionary context where possible. Priorities for further taxonomic, phylogenetic and biogeographic research are listed and discussed. We predict that within a decade the phylogeny of all European species will be known.     

Biomanipulation additional to nutrient control for restoration of shallow lakes in The Netherlands

Eutrophication control is one of the major issues in the environmental policy in The Netherlands. As a result of international action programmes the average phosphorus loading of freshwater systems should decrease by 50% between 1985 and 1995. However, in many cases the restoration of water quality requires additional measures. Recovery is hampered by the structure and functioning of the present food-chain.

The feeding behaviour of the dominant fish species in Dutch lakes, bream and roach, tend to impose a homeostasis on the system, resisting restoration of water quality. In shallow lakes, biomanipulation, including drastic reduction of fish-stocks, may induce a shift from a stable ‘turbid-water state’ to a stable ‘clear-water state’.

To assess the possibilities of biomanipulation for the restoration of a particular lake, three questions are relevant: (1) is a drastic reduction of fish-stocks feasible?, (2) will a shift occur from ‘turbid to clear’ after the fish reduction? and (3) will the new situation of clear water be stable? This paper focuses attention on the last two questions. The increase in water clarity, following fish reduction, largely depends on the increase in the density of the Daphnia-population and the contribution of benthivorous fish to the resuspension of sediments. A ‘turbid to clear’ shift may be expected if the total biomass of planktivorous and benthivorous fish is reduced to levels<50 kg ha^?1. The stability of the achieved clear-water state largely depends on the development of submerged macrophytes in the lake and on the level of nutrient loading. It is tentatively concluded that a stable clear-water state may be expected at initial total-P concentrations<0.10 mg l^?1.

Because the water managers in The Netherlands have no fishing rights, they have to.co-operate with anglers and commercial fishermen to apply biomanipulation as a tool for water management.

     

综述: 果蝇复杂脑功能研究进展

全面揭示脑的奥秘是现代科学所面临的最大挑战.通过脑研究,我们可以获得防治脑疾病、认知及心理障碍的线索和工具,找到提高人类智力和心理健康水平的途径,并发展出具备高等智能的机器人.果蝇作为研究基因-神经回路-行为关系的首选模式动物,日益得到重视.本文围绕果蝇复杂脑功能包括视觉学习记忆、欲望与动机、情感相关行为和社会行为的研究意义及前景、已知调控基因及神经回路以及未来研究方向展开综述,便于读者把握相关领域的全貌.     

Understanding DNA Conformational Dynamics: Answering Questions and Questioning Answers

Abstract

Phosphorus-31 and especially Carbon-13 NMR measurements have recently become primary input to the understanding of DNA solution dynamics. While the ³¹P measurements are inherently easier, the quality of ³¹P dynamics information is suspect and therefore ¹³C measurements are preferred. In fact, it is necessary to obtain several kinds of ¹³C data (T₁s, NOE's, linewidths, integrated peak intensities) over a wide range of magnetic fields (¹³C NMR frequencies) in order to identify major features of DNA internal motions. Further information comes from variation of temperature and DNA fragment length and/or concentration. Most of our ¹³C measurements have been performed at 37.7–90.6 MHz on fully double stranded monomer size (147 base pair) DNA at concentrations in phosphate buffer of < 10 to > 200 mg ml^?1; temperatures studied range from 6 to 55°C. Other measurements have been performed on monomer-size single-stranded DNA at 85 and 92°.

The large data set we have acquired appears to answer some important questions about the nature and extent of DNA overall and internal motional dynamics. However, the picture remains incomplete and a number of questions arise from these results:

1. Overall motion of the double stranded DNA fragments follows expected hydrodynamic behavior;

2. Restricted but rapid internal motion along the DNA structure is well represented by a spaghetti-like wobbling-in-a-cone model;

3. DNA-DNA Interactions and solvent ordering, present at relatively low DNA concentrations, partially quench the internal motion, consistent with hinge-model structural changes (and the spaghetti model above) but not as compatible with in-plane torsional motion models;

4. The deoxyribose C-2′ sites undergo additional motion which is partially uncoupled from the internal wobbling motions;

5. At high DNA concentrations, a phase transition occurs, resulting in ordered structures which drastically affect DNA internal dynamics;

6. DNA interacting with ethidium does not greatly change its conformational mobility;

7. DNA interacting with Hg²⁺ ions shows less than anticipated change in internal DNA dynamics.

The remaining challenge is to interpret our current results in terms of specific conformational processes and to understand why the conformational mobility of double stranded DNA is relatively unhindered by major structural perturbants such as intercalating ethidium and mercury ion.     

Beyond global change: lessons from 25 years of CO2 research

Over the past 25 years, countless experiments have been conducted on the impact of increased atmospheric CO₂ concentration on various plants and ecosystems. While this research was motivated to better understand and predict how rising CO₂ will affect the structure and function of ecosystems in the future, it also shed light on some general, CO₂-research independent, aspects in ecological research. Interestingly, it is these general aspects that continue to create confusion and lead to misinterpretation. Here, we focus on seven interrelated key issues including (1) the confusion between fluxes and pools, (2) the stoichiometric aspects of growth and biomass production, (3) resource allocation within organisms, (4) data scaling and the choice of a reference metric, (5) the consideration of time and timing (experimental duration, ontogenetic shifts), (6) confounding and second-order (indirect or feedback) effects, and (7) the key role of biodiversity. The principles deriving from addressing these issues relate strongly to each other. Their concurrent consideration requires experimenters and modellers to likewise maintain a broad, holistic perspective. In this synthesis, we attempt to show how appropriate consideration of these principles can greatly enhance the assessment of the validity, plausibility and generality of experimental and modelling results. We conclude that neglecting to adequately address these key issues in ecological research may lead to overestimations of measured responses and/or simplistic interpretations. Our examples mostly originate from research on plant responses to elevated atmospheric CO₂, but are also applicable to other areas of ecological research. We provide a checklist for the planning of ecological field experiments and the interpretation of their results that may help in avoiding common pitfalls.     

Actions of Ca2+ on an Early Stage in Phototransduction Revealed by the Dynamic Fall in Ca2+ Concentration during the Bright Flash Response

To study the actions of Ca²⁺ on “early” stages of the transduction cascade, changes in cytoplasmic calcium concentration (Ca²⁺ _i) were opposed by manipulating Ca²⁺ fluxes across the rod outer segment membrane immediately following a bright flash. If the outer segment was exposed to 0 Ca²⁺/0 Na⁺ solution for a brief period immediately after the flash, then the period of response saturation was prolonged in comparison with that in Ringer solution. But if the exposure to 0 Ca²⁺/0 Na⁺ solution instead came before or was delayed until 1 s after the flash then it had little effect. The degree of response prolongation increased with the duration of the exposure to 0 Ca²⁺/0 Na⁺ solution, revealing a time constant of 0.49 ± 0.03 s. By the time the response begins to recover from saturation, Ca²⁺ _i seems likely to have fallen to a similar level in each case. Therefore the prolongation of the response when Ca²⁺ _i was prevented from changing immediately after the flash seems likely to reflect the abolition of actions of the usual dynamic fall in Ca²⁺ _i on an early stage in the transduction cascade at a site which is available for only a brief period after the flash. One possibility is that the observed time constant corresponds to the phosphorylation of photoisomerized rhodopsin.     

Oxygen poisoning in Drosophila

Fruit flies live longer at the partial pressure of oxygen found in air than at either larger or smaller partial pressures. Flies exposed to 1 atm of oxygen for 8 hr every day do not recover completely in the remaining 16 hr. In general, intermittent exposures to 1 atm of oxygen are better tolerated than continuous exposure to the same average oxygen concentration per day, but exposures to higher pressures of 2–5 atm of oxygen for as little as a half hour every two days markedly shorten the life-span. Older flies consume more oxygen per minute and are more sensitive to oxygen poisoning than young flies, and the rate of dying in 6 atm of O₂, or the reciprocal of the survival time, is a linear function of the age. The oxygen pressure-time curve can be well expressed by the general empirical equation (P_OO2)² x time = 120 where P is in atmosphere and survival time in hours. The progress of oxygen poisoning appears to be linear with time rather than exponential.     

中国电力行业CO2减排潜力及其贡献因素

电力行业低碳转型是中国低碳经济转型进程中关键行业之一,如何科学分析电力行业的碳减排潜力,确定操作性强的低碳转型路线、提出有效的政策措施是中国政府亟待解决的焦点问题之一。考虑终端电力消费、低碳能源发电占比、火力发电结构、火力发电效率、线损率等因素,构建了自底向上的电力行业CO2排放核算模型,在此基础上,利用情景分析方法探索中国电力行业2015和2020年的CO2减排潜力,进一步利用对数平均权重分解法(LMDI,Logarithmic Mean weight Divisia Index method)对电力行业CO2减排影响因素的贡献度做了归因分析。结果显示,相比基准情景,在当前政策情景和低碳政策情景下,电力行业将分别带来27.0亿t和36.9亿t的CO2减排量。低碳能源发电和火力发电效率是未来对CO2减排最重要的两个贡献因素。终端电力消费量一直是促进电力行业CO2排放增长最重要的贡献因素,因此通过电力需求侧管理等手段控制电力消费量对电力行业的低碳发展至关重要。最后结合减排贡献因素分析的结果为中国电力行业低碳发展提出了相应的政策建议。     

土壤呼吸的温度敏感性——全球变暖正负反馈的不确定因素

基于模型模拟结果表明,全球变暖与大气CO2浓度增加将形成正反馈关系,这种正反馈效应将明显加速21世纪的气候变暖。然而,这些模拟模型都基于一个重要假设,即不同平均驻留时间的土壤有机质分解具有相同的温度敏感性(Q10)。这一假设与酶动力学理论相悖,而且不同学者对不同质量土壤有机质分解温度敏感性的差异的认识存在严重分歧,所以,全球变暖与大气CO2浓度增加的正反馈关系的显著性仍值得商榷。围绕土壤呼吸的温度敏感性问题进行了讨论和评述,涉及1)土壤有机质分解温度敏感性争论的焦点问题;2)通过经验模型曲线拟合估计Q10值存在的分歧及Q10变异的机理解释;3)实验室土壤培养实验估计Q10值存在的问题;4)土壤培养实验中Q10值计算方法的改进。进一步深化有关土壤有机质分解温度敏感性不确定性的认识,将为今后土壤呼吸及其对气候变化响应的相关研究提供参考。     

Recent advances on the structure and function of NDH-1: The complex I of oxygenic photosynthesis

Photosynthetic NADH dehydrogenase-like complex type-1 (a.k.a, NDH, NDH-1, or NDH-1L) is a multi-subunit, membrane-bound oxidoreductase related to the respiratory complex I. Although originally discovered 30 years ago, a number of recent advances have revealed significant insight into the structure, function, and physiology of NDH-1. Here, we highlight progress in understanding the function of NDH-1 in the photosynthetic light reactions of both cyanobacteria and chloroplasts from biochemical and structural perspectives. We further examine the cyanobacterial-specific forms of NDH-1 that possess vectorial carbonic anhydrase (vCA) activity and function in the CO₂-concentrating mechanism (CCM). We compare the proposed mechanism for the cyanobacterial NDH-1 vCA-activity to that of the DAB (DABs accumulates bicarbonate) complex, another putative vCA. Finally, we discuss both new and remaining questions pertaining to the mechanisms of NDH-1 complexes in light of these recent advances.     

Synthetic biology for CO2 fixation

Recycling of carbon dioxide (CO₂) into fuels and chemicals is a potential approach to reduce CO₂ emission and fossil-fuel consumption. Autotrophic microbes can utilize energy from light, hydrogen, or sulfur to assimilate atmospheric CO₂ into organic compounds at ambient temperature and pressure. This provides a feasible way for biological production of fuels and chemicals from CO₂ under normal conditions. Recently great progress has been made in this research area, and dozens of CO₂-derived fuels and chemicals have been reported to be synthesized by autotrophic microbes. This is accompanied by investigations into natural CO₂-fixation pathways and the rapid development of new technologies in synthetic biology. This review first summarizes the six natural CO₂-fixation pathways reported to date, followed by an overview of recent progress in the design and engineering of CO₂-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 CO₂.     

Present State and Future Perspectives of Prostaglandins as a Differentiation Factor in Motor Neurons

Spinal motor neurons have the longest axons that innervate the skeletal muscles of the central nervous system. Motor neuron diseases caused by spinal motor neuron cell death are incurable due to the unique and irreplaceable nature of their neural circuits. Understanding the mechanisms of neurogenesis, neuritogenesis, and synaptogenesis in motor neurons will allow investigators to develop new in vitro models and regenerative therapies for motor neuron diseases. In particular, small molecules can directly reprogram and convert into neural stem cells and neurons, and promote neuron-like cell differentiation. Prostaglandins are known to have a role in the differentiation and tissue regeneration of several cell types and organs. However, the involvement of prostaglandins in the differentiation of motor neurons from neural stem cells is poorly understood. The general cell line used in research on motor neuron diseases is the mouse neuroblastoma and spinal motor neuron fusion cell line NSC-34. Recently, our laboratory reported that prostaglandin E₂ and prostaglandin D₂ enhanced the conversion of NSC-34 cells into motor neuron-like cells with neurite outgrowth. Moreover, we found that prostaglandin E₂-differentiated NSC-34 cells had physiological and electrophysiological properties of mature motor neurons. In this review article, we provide contemporary evidence on the effects of prostaglandins, particularly prostaglandin E₂ and prostaglandin D₂, on differentiation and neural conversion. We also discuss the potential of prostaglandins as candidates for the development of new therapeutic drugs for motor neuron diseases.

     

Memory enhancement: the progress and our fears

In a recent article Rose (2002) raises numerous crucial issues with regard to the research into and the use of cognition or memory enhancing agents. Although development of 'smart' drugs is in its infancy, his paper delineates some issues society may have to face when these drugs arrive. Questions about the development of such drugs may be interesting to several readers of Genes Brain and Behavior given the wealth of information expected to be gained on brain function from studies using genetic approaches including mutagenesis, transgenic techniques and genomics in general. Besides the scientific questions, several ethical issues may need to be addressed that are of interest to us all. Rose (2002 ) discusses some of these questions, but perhaps presents a too negative view on the problems, especially with regard to the present and future of memory research. This paper is intended to focus mainly on the scientific questions and argues that our fear of complex ethical problems should not make us throw the baby (i.e., our research and discoveries) out with the bath water.     

Effects of removal and reconstitution of the extrinsic 33, 24 and 16 kDa proteins on flash oxygen yield in Photosystem II particles

The effects of removal and reconstitution of the three extrinsic proteins on the flash O₂ yield were investigated and the following results were obtained. (1) Removal in darkness of the 24 and 16 kDa proteins affected neither the oscillation pattern nor the signal amplitude of the flash O₂ yield. However, the signal amplitude was reduced with a factor of 2 in the presence of EDTA and was restored by excess Ca²⁺. The EDTA treatment did not change the oscillation pattern of the flash O₂ yield, but considerably damped the oscillation pattern of thermoluminescence B band. These results suggest a heterogeneity among the centers in binding affinity for Ca²⁺, and that Ca²⁺ removal induces an all-or-none type inactivation of O₂ evolution but not in the thermoluminescence processes, indicative of an inhibition of the S-state turnover at a specific S-state. (2) Removal in darkness of the 33, 24 and 16 kDa proteins abolished the flash O₂ yield, but the inhibited yield was appreciably restored either by reconstitution with the 33 kDa protein or by inclusion of 200 mM Cl⁻ in the reaction mixture. The flash O₂ yield reconstituted by the 33 kDa protein exhibited a rather normal oscillation pattern accompanied by a slightly increased damping, which could be simulated by assuming a high miss factor (30%) for S₃ → S₀ transition. The Cl⁻-restored flash O₂ yield exhibited a strongly damped oscillation pattern with obscured maxima at the 4th and 8th flashes, which was simulated by assuming a much higher miss factor (70%) for S₃ → S₀ transition. It was indicated that the Cl⁻-restored O₂ evolution considerably differs from the 33 kDa protein-reconstituted O₂ evolution with respect to the mechanism of S-state turnover.     

CO2‐Mediated H2 Storage‐Release with Nanostructured Catalysts: Recent Progresses,Challenges, and Perspectives

It has increasingly become clear that economic growth worldwide based on fossil fuel energy supply cannot be sustained; thus, alternative, renewable energy sources and carriers must be urgently developed to maintain growth. Dihydrogen (H₂), which can produce energy without generating environmental pollutants, can play a major role in this endeavor. However, to use H₂ in renewable energy systems, systems and materials that can store and transport it, or convert it into easier‐to‐handle/transport synthetic fuels, need to be developed. In this article, first, many of the issues related to both homogeneous and heterogeneous catalysts that are being developed to help H₂'s use as energy carrier are discussed. More focus is then given to heterogeneous nanocatalysts that are developed for reversible CO₂‐mediated hydrogenation and dehydrogenation reactions involving chemical hydrogen carriers and delivery systems, mainly formic acid/CO₂ and formate/bicarbonate. The challenges associated with the development of nanocatalysts based on earth‐abundant elements for dehydrogenation and hydrogenation reactions of these compounds for H₂ storage and release are emphasized in the discussions. Finally, the pressing research questions and major issues that need to be addressed in the near future to help the realization of the “hydrogen economy” are outlined.     

Reduction kinetics of the photo-oxidized chlorophyll a+II in the nanosecond range: Measurements of the absorption changes at 688 nm under repetitive flash excitation

The 688 nm absorption changes (ΔA₆₈₈), indicating the photochemical turnover of chlorophyll a_II (Chl a_II) have been investigated under repetitive laser flash excitation conditions in spinach chlorplasts. It was found that under steady state conditions about 50–60% of the photo-oxidized primary donor of Photosystem II (PS II), Chl a⁺_II, becomes re-reduced with a biphasic kinetics in the nanosecond time scale with half-life times of about 50 ns and 400 ns. The remaining Chl a⁺_II becomes re-reduced in the microsecond range.