青藏高原东部高山植物的水分利用效率与氮素利用效率研究

对生长在青藏高原东部隶属于23科、49属的71种高山植物(包括多年生和一年生植物)的稳定碳同位素比值、氮含量以及碳/氮比率进行了分析,并以稳定碳同位素比值及碳/氮比率来分别指示植物的水分利用效率和氮素利用效率.结果表明:(1)多年生植物稳定碳同位素比值显著高于一生年植物,而碳/氮比率显著低于一年生植物(P<0.01),氮含量两者无显著性差异.(2)多年生植物和一年生植物的稳定碳同位素比值均与碳/氮比率呈显著负相关(-0.643**和-0.707),而与氮含量均无明显相关性.研究证实,在自然条件下多年生植物的水分利用效率比一年生植物更高,而氮素利用效率却更低;高山植物水分利用效率和氮素利用效率存在明显的权衡",即植物不能同时提高水分利用效率和氮素利用效率,高水分利用效率的代价是降低氮素利用效率,青藏高原不同植物即使在相同环境条件下具有不同适应对策.     

小麦进化材料水分利用效率与氮利用效率间相互关系

利用田间微区试验,在整株水平上研究了10种小麦进化材料水分利用效率(WUE)和氮利用效率(NUE)间的关系．结果表明,小麦在从二倍体→六倍体的长期进化过程中,WUE和NUE均逐渐增加．除法国黑麦外,其余9种小麦进化材料WUE和NUE间呈显著正相关,表明法国黑麦高的NUE可能与WUE以外的其它生理机制有关．     

农田光能利用效率研究进展

光能利用率(RUE)是作物生长模型的主要参数之一.RUE被广泛应用于基于遥感的净初级生产力估算.受环境条件影响,作物生长季内RUE并非常数.RUE估算不准将给净初级生产力的模拟计算带来很大误差.本文分析了农田RUE的测定方法和变化特征.讨论了辐射、温度、饱和差、植物叶片氮含量和作物种类对RUE的影响,分析了目前RUE研究中存在的问题,提出在作物模型中用RUE作参数时必须考虑作物生长发育所引起的RUE变化.今后应加强作物生物量和截获辐射间关系的机理研究.利用涡度相关技术等微气象方法研究短时间尺度上RUE的变化将成为未来研究的热点.     

陆生植物水分利用效率

植物水分利用效率（water use efficiency,WUE）作为叶片光合与水分生理过程的耦合因子,不仅是联系植被生态系统碳循环与水循环的重要变量,同时亦已成为揭示陆地植被生态系统对全球变化响应和适应对策的重要手段。稳定同位素技术和涡度相关技术的发展和应用,使植物WUE的概念和测定方法不断得到扩展,研究内容、尺度也不断拓宽。深入认识植物WUE的变化特征及其调控机制,一方面有助于揭示不同植物对生境的生理生态适应机理,另一方面能够促进对陆地生态系统碳-水平衡关系的理解。目前生态系统水平WUE的研究尚处初始阶段。如何建立不同尺度水平WUE间的联系机制,将成为今后该研究领域的关注点。本文在阐述植物WUE概念和测定方法的基础上,综述了植物叶片水平WUE的影响因子、种间差异与水分利用策略,以及WUE与其他叶性状的关系,介绍了当前生态系统水平WUE的研究状况,提出未来的研究趋势。     

生态系统水分利用效率研究进展

水分利用效率(WUE)是反映生态系统水碳循环相互关系的重要指标,开展生态系统水平WUE的时空变异性的研究有助于预测气候变化对生态系统水碳过程的影响.目前不同研究常常基于不同的算法估算生态系统WUE,一方面不同算法因包含了不同复杂程度的水过程而有着不同的内涵,另一方面各种算法又因包含了相同的核心过程而有着密切的联系.长期以来人们通过传统的生物量动态调查和生态系统水文过程的测定来估算生态系统的WUE,但该方法大大限制了在短时间尺度上对生态系统WUE进行分析,近年来发展起来的以涡度相关为代表的新技术的应用使得研究生态系统WUE在多个时空尺度上的变异特征取得了突破性的进展.生态系统WUE的主要影响因子与叶片尺度相似,主要有空气饱和水气压差(VPD)、土壤水分、大气CO2浓度、Ci/Ca等,另外,生态系统水分平衡特征也有着重要影响.比较分析表明,森林与草地生态系统WUE的日变化和季节变化存在显著的差异,同时森林和农田生态系统的WUE整体高于草地、荒漠和冻原.当前生态系统WUE的研究尚处于初始阶段,许多工作仍需深入开展,其中,多时间尺度以及生态系统间WUE的时空变异特征及机理的对比研究可能是未来工作的热点.     

刺槐人工林养分利用效率

目前普遍采用的短轮伐期萌生复壮的经营方式会使刺槐人工林在多代萌生以后地力衰退,生产力下降,其主要原因是由于树种对养分的选择吸收导致土壤养分平均失调。根据对黄土残塬沟壑区刺槐人工林地的研究表明,刺槐从土壤中年吸收养分量以Ca最多,N次之,K、Mg再次,P、S最少,且随树龄增长年吸收量增大,由速生期到杆材期年吸收量约增加1倍之多,由杆材期到成熟期N、P、K、Mg年吸收量缓慢增加,而Ca,S的吸收量有所下降,土壤养分年吸收系数以N最高,S、Mg次之,P、Ca再次,K最多,且随树龄的增长亦呈增大趋势,其均值分别可达N1．150％、P0．142％、K0．013％、Ca0．110％、Mg0.194%、S0．231％。刺槐对各养分的利用效率随树龄的增长而降低,生产1t树干材积约需从土壤中吸收N31．92－50．88kg,P1.32-2.01kg,K4.48-6.82kg,Ca71.57-78.79kg,Mg6.16-9.74kg,S1.07-1.09kg,立地条件好的林地养分吸收系数及养分利用效率均好于立地条件较差的林地。此外与杉木,油松相比,刺槐对养分的利用效率明显偏低。     

玉米叶片水分利用效率的保守性

水分利用效率是植物个体或生态系统水分利用过程的重要特征参数,可表征不同时空尺度的植物碳-水耦合关系,对植物适应气候变化研究具有重要意义。以玉米为例,利用中国气象局固城农业气象野外科学试验基地2013—2014年玉米不同灌溉方案模拟试验资料,对不同叶位叶片的水分利用效率特征及其影响因素进行分析。结果表明:植株顶部第1片叶片水分利用效率在拔节期和乳熟期呈现明显的峰值,反映出明显的周期变化规律及其与叶片生理生态特征的紧密相关。在相同环境条件下,不同叶位叶片的水分利用效率不存在显著性差异,即玉米叶片水分利用效率具有空间稳定性与叶龄保守性。同时,研究指出叶片光合速率和蒸腾速率在叶位之间的协调变化是导致空间稳定性和叶龄保守性的主要原因。研究结果可为植物水分关系研究提供参考,也可为水分利用效率的尺度化研究提供依据。     

提高农田水分利用效率的途径

水分利用效率（WUE）,系指植物消耗单位水量生产出的同化量,它反映植物生产中的能量转化效率,同时也是评价缺水条件下植物生长适宜程度的一个指标。WUE可在不同层次上表述：在单叶水平上,WUE以净光合速率（Pn）与蒸腾速率（T）之比（Pn／T）来表示;在田间群体水平上则通常以地上部干物质量［产量,干重（yet）］与蒸腾蒸发（sr）之比〔干重（yet）／crj来表示。在半干旱低产条件下,农田蒸腾水的消耗仅占到降水量的一小部分,通过ET的消耗也仅占到降水量的一半或稍多,其余则消耗于径流、渗漏及蒸发。由此,出现了降水利用率（R…     

小麦氮素利用效率的基因型差异

通过土培盆栽试验,研究了130份小麦材料在相同氮素水平下生物量、氮素积累量、氮素生产效率的基因型差异,旨在筛选具有高效利用氮素能力的小麦基因型,为氮高效小麦育种提供种质资源.结果表明:拔节期、抽穗期和成熟期供试小麦单株生物量变幅分别为1.06～3.08 g、1.88～9.05 g和2.64～13.75 g,单株籽粒产量变幅为1.38～9.90 g.拔节期、抽穗期氮素干物质生产效率变幅分别为25.62～65.41 g.g-1 N(F=5.099**)和35.79～88.70 g·g-1 N(F=5.325**),成熟期氮素籽粒生产效率变幅为19.06～38.54 g.g-1 N(F=4.669**).不同氮素生产效率小麦基因型拔节期氮素干物质生产效率(F=637.941**)、抽穗期氮素干物质生产效率(F=201.173**)及成熟期氮素籽粒生产效率(F=443.450**)存在极显著差异.不同氮素生产效率小麦基因型拔节期、抽穗期及成熟期生物量差异显著,有效分蘖数与穗数差异不显著.氮素生产效率高的基因型具有无效分蘖少、抽穗期前氮素利用能力强、抽穗期-成熟期氮素吸收与再利用能力强等特点.典型氮高效基因型小麦省CX...     

小麦磷素利用效率的品种差异

通过土培盆栽试验,研究了小麦不同品种在低磷水平下生物量、磷浓度、磷素干物质生产效率及磷素籽粒生产效率的差异,以筛选磷高效利用小麦品种.结果表明：分蘖期、拔节期、扬花期和成熟期,供试小麦品种单株生物量的变幅分别为0.46～1.09、0.85～2.10、3.00～7.00和3.85～12.88 g,磷浓度变幅分别为2.21～4.26、2.38～4.42、2.44～4.96和1.30～5.09 mg·g^-1.随生育时期的推进,小麦磷素累积量、磷素干物质生产效率对生物量形成的影响程度呈减小趋势.分蘖期（CV=16.3%）、拔节期（CV=15.0%）、扬花期磷素干物质生产效率（CV=13.3%）和成熟期磷素籽粒生产效率（CV=20.5%）的品种差异较大.CD1158-7和省A3宜03-4具有较高的磷素干物质生产效率和磷素籽粒生产效率,而渝02321较低;不同生育时期高效品种磷浓度极显著低于低效品种,而高效品种CD1158-7和省A3宜03-4的籽粒产量分别是低效品种渝02321的1.98和1.78倍.     

Thirty Years of Luminescent Solar Concentrator Research: Solar Energy for the Built Environment

Research on the luminescent solar concentrator (LSC) over the past thirty‐odd years is reviewed. The LSC is a simple device at its heart, employing a polymeric or glass waveguide and luminescent molecules to generate electricity from sunlight when attached to a photovoltaic cell. The LSC has the potential to find extended use in an area traditionally difficult for effective use of regular photovoltaic panels: the built environment. The LSC is a device very flexible in its design, with a variety of possible shapes and colors. The primary challenge faced by the devices is increasing their photon‐to‐electron conversion efficiencies. A number of laboratories are working to improve the efficiency and lifetime of the LSC device, with the ultimate goal of commercializing the devices within a few years. The topics covered here relate to the efforts for reducing losses in these devices. These include studies of novel luminophores, including organic fluorescent dyes, inorganic phosphors, and quantum dots. Ways to limit the surface and internal losses are also discussed, including using organic and inorganic‐based selective mirrors which allow sunlight in but reflect luminophore‐emitted light, plasmonic structures to enhance emissions, novel photovoltaics, alignment of the luminophores to manipulate the path of the emitted light, and patterning of the dye layer to improve emission efficiency. Finally, some possible ‘glimpses of the future’ are offered, with additional research paths that could result in a device that makes solar energy a ubiquitous part of the urban setting, finding use as sound barriers, bus‐stop roofs, awnings, windows, paving, or siding tiles.     

GaSb‐Based Solar Cells for Full Solar Spectrum Energy Harvesting

In this work, a multijunction solar cell is developed on a GaSb substrate that can efficiently convert the long‐wavelength photons typically lost in a multijunction solar cell into electricity. A combination of modeling and experimental device development is used to optimize the performance of a dual junction GaSb/InGaAsSb concentrator solar cell. Using transfer printing, a commercially available GaAs‐based triple junction cell is stacked mechanically with the GaSb‐based materials to create a four‐terminal, five junction cell with a spectral response range covering the region containing >99% of the available direct‐beam power from the Sun reaching the surface of the Earth. The cell is assembled in a mini‐module with a geometric concentration ratio of 744 suns on a two‐axis tracking system and demonstrated a combined module efficiency of 41.2%, measured outdoors in Durham, NC. Taking into account the measured transmission of the optics gives an implied cell efficiency of 44.5%.     

Liquid Norbornadiene Photoswitches for Solar Energy Storage

Due to high global energy demands, there is a great need for development of technologies for exploiting and storing solar energy. Closed cycle systems for storage of solar energy have been suggested, based on absorption of photons in photoresponsive molecules, followed by on‐demand release of thermal energy. These materials are called solar thermal fuels (STFs) or molecular solar thermal (MOST) energy storage systems. To achieve high energy densities, ideal MOST systems are required either in solid or liquid forms. In the case of the latter, neat high performing liquid materials have not been demonstrated to date. Here is presented a set of neat liquid norbornadiene derivatives for MOST applications and their characterization in toluene solutions and neat samples. Their synthesis is in most cases based on solvent‐free Diels‐Alder reactions, which easily and efficiently afford a range of compounds. The shear viscosity of the obtained molecules is close to that of colza oil, and they can absorb up to 10% of the solar spectrum with a measured energy storage density of up to 577 kJ/kg corresponding to 152 kJ mol^–1 (calculated 100 kJ mol^–1). These findings pave the way towards implementation of liquid norbornadienes in closed cycle energy storage technologies.     

Utilization of Energy Nutrients by Cerebellar Slices

We performed an ontogenetic study about the utilization of glycine, glutamine, -hydroxybutyrate and glycerol as energy nutrients by rat cerebellum slices. Production of CO₂ from glycerol and glutamine increased with the animals' age and glutamine was the most used nutrient for CO₂ production. In adult age, glutamine oxidation to CO₂ was 15 to 35 times higher than all other nutrients studied. CO₂ production from glycine decreased markedly with age and 10 day-old rats showed an oxidation 7.5 times higher than that of adult rats. At fetal age and at 10 postnatal days, glycine oxidation to CO₂ was only 2 times lower than glutamine oxidation to CO₂. Lipid synthesis from -hydroxybutyrate was highest in adult rats. We did not observe any difference in the utilization of -hydroxybutyrate between slices of cerebral cortex and cerebellum at the ages of 10 days and adult. The main nutrients used for lipid synthesis were glycerol and -hydroxybutyrate.     

Graphene Based Materials: Enhancing Solar Energy Harvesting

Due to excellent electronic and optical properties as well as tunable work functions, graphene and graphene‐based materials are highly attractive for applications in enhancement of harvesting solar energy. In particular, they can be used as electron and hole transport materials, buffer layers, and window or/and counter electrodes in solar cells. This research news surveys very recent advances in this emerging field, with emphasis on fundamental understanding of their performance enhancement mechanisms for photovoltaic devices, and discusses future challenges.