氮素类型和剂量对寒温带针叶林土壤N2O排放的影响

大气氮沉降输入会增加森林生态系统氮素有效性,进而改变土壤N_2O产生与排放,然而有关不同氮素离子(氧化态NO_3~--N与还原态NH_4~+-N)沉降对土壤N_2O排放的影响知之甚少。以大兴安岭寒温带针叶林为研究对象,构建了3种类型(NH_4Cl、KNO_3、NH_4NO_3)和4个施氮水平(0、10、20、40 kg N hm~(-2)a~(-1))的增氮控制试验,利用流动化学分析仪和静态箱-气相色谱法4次/月测定凋落物层和矿质层土壤无机氮含量、土壤-大气界面N_2O净交换通量以及相关环境因子,分析施氮类型和剂量对土壤氮素有效性、土壤N_2O通量的影响探讨氮素富集条件下土壤N_2O通量的环境驱动机制。结果表明:施氮类型和剂量均显著影响土壤无机氮含量,土壤NH_4~+-N的积累效应显著高于NO_3~--N。施氮一致增加寒温带针叶林土壤N_2O排放,NH_4NO_3促进效应最为明显,增幅为442%-677%,高于全球平均水平(134%)。土壤N_2O通量与土壤温度、凋落物层NH_4~+-N含量正相关,且随着施氮水平增加而增加。结果表明大气氮沉降短期内不会导致寒温带针叶林土壤NO_3~--N大量流失,但会显著促进土壤N_2O的排放。此外,外源性NH_4~+和NO_3~-输入对土壤N_2O排放的促进作用具有协同效应,在未来森林生态系统氮循环和氮平衡研究中应该区分对待。     

烟草镉的富集及防控措施研究进展

烟草是富镉耐镉作物,降低烟叶镉含量对人体健康十分重要。从烟草镉含量、烟草镉富集及其影响因素、烟草镉防控措施三方面进行了综述,系统分析了该研究领域的成果、现状和存在问题,并对未来烟叶控镉的工作方向进行了展望,以期为低镉烟叶生产提供参考。     

用性信息素诱剂防治烟青虫的效果

本文研究了两个烟青虫性信息素诱剂配方对烟青虫Helicoverpaassulta (Guen e)成虫的诱杀效果及诱杀成虫后田间烟青虫幼虫的虫口减退率和有虫株减退率。 1型诱芯配比为Z9 1 6 :Ald与Z1 1 1 6 :Ald 1 0 0∶9 5 ;Ⅱ型诱芯配比为 1 6 :Ald和Z9 1 6 :Ald与Z1 1 1 6 :Ald( 1 9 3∶1 0 0∶70 )。结果表明 :烟青虫性信息素诱剂Ⅰ ,Ⅱ型诱芯对烟青虫成虫都有很强的诱杀效果 ,在长达 85d的时间内 ,5个Ⅰ型诱芯共诱杀了4 0 4头雄性成虫 ,5个Ⅱ型诱芯共诱杀 4 1 9头 ,二者没有明显的差异。诱蛾地烟青虫幼虫的虫口密度和有虫株率都有明显的降低 ,Ⅰ、Ⅱ型诱芯使虫口密度和有虫株率的降低幅度均在 6 6 6 7%～ 90 91 %之间。性信息素诱剂使用方便、无毒、不污染环境 ,对烟叶不产生药害 ,防治效果良好 ,具有良好的应用前景。     

Modeling of Actual Eukaryotic Control Gene Subnetworks Based on the Method of Generalized Threshold Models

Mathematical and computational means are developed that take into consideration the specifics of control processes at the molecular level and allow one to obtain both qualitative and quantitative patterns of gene network dynamics. Using the method of generalized threshold models, models are constructed for the Arabidopsis thalianaflower morphogenesis control subsystem and gene subnetwork controlling the Drosophila melanogasterearly ontogeny. The dynamics of these systems are investigated: kinetic curves are computed for molecular components (RNA, proteins), possible modes of functioning and steady states of the nets are revealed and biologically interpreted. The models are shown to be adequate to the real processes. The effectiveness of the generalized threshold model method is evaluated in the analysis of the actual eukaryotic gene networks.     

土壤酸化过程的土壤化学分析

要了解自然的抑或农业的土壤生态系统,认识和研究土壤酸化过程是必要的。土壤酸化过程在自然界是固然存在的,它们是地壳表面     

学习行为实验控制仪

本文介绍一种可以控制分辨学习、条件反射及交互延缓等行为实验的仪器,它采用脉冲数字电路,具有“自动”和“手控”两种工作方式。它能鉴别受试者所作反应的正确或错误,并发出相应信号供记录之用,本仪器为研究与学习行为有关的中枢神经系统电活动提供了不少方便,不仅可以节省人力还可以使实验结果更为可靠。     

The three dimensional distribution of the fauna in a single riffle in a stream in Ontario

The surface and hyporheic fauna of a riffle area in Salem Creek near Elmira, Ontario, was investigated with a Surber and a corer sampler. A stratified random sampling design estimated the number of invertebrates at 154 561 (109 805–224 155) m^–2 in June and at 64 407 (40 905–97 996) m^–2 in October with more than 70% of the animals occurring below 5 cm. There was a great spatial variation of the hyporheos density in the three dimensions of the riffle, which seemed to be related mostly to hydrogeological characteristics (superficial groundwater flow and grain size). Upward water movement in the centre of the stream occurred in the upper two transects, especially from the upper right bank, while the lower transect showed little water transmission. Hyporheos composition is discussed in regard to life history and the input of organic materials. Only two of nine pairs of Surber samples showed a high degree of similarity (0.68, 0.81). The surficial spatial density and diversity were examined in relation to the available surface and to substrate heterogeneity. It is concluded that the great variations between samples caused by many factors present severe problems in the collection of reliable quantitative samples.

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Résumé La faune de surface et celle de l'hyporhélique d'un radier de Salem Creek près d'Elmira, Ontario, ont été étudiées à l'aide de l'échantillonneur de Surber et d'un carottier. Un échantillonnage aléatoire stratifié a permis d'estimer le nombre d'invertébrés a 154 561 (109 805–224 155) m^–2 en juin et à 64 407 (40 905–97 996) m^–2 en octobre. Environ 70% de la faune benthique a été retrouvée entre 5 et 65 cm. La densité de l'hyporhéos présente de grandes variations spatiales, et celles-ci semblent etre reliées aux caractéristiques hydrogéologiques (mouvement des eaux souterraines superficielles et taille des particules). Un net mouvement ascendant dirigé vers le centre du radier a été détecté dans les deux transects situés en amont; aucun mouvement n'a été mesuré dans un troisième transect situé an aval. La composition de l'hyporhéos est mise en relation avec les cycles vitaux et avec l'apport des matières organiques. Des 9 paires d'échantillons recueillis au Surber, deux seulement présentent un certain degré de similarité (0.68, 0.81). Les variations spatiales de la densité et de la diversité de la faune de surface furent mises en corrélation avec la surface disponible et l'hétérogénéité du substrat. On en conclu que la grande variabilité entre les échantillons dans les deux habitats est due à plusieurs facteurs et qu'elle pose de sérieux problèms pour l'estimation de paramètres quantitatifs.

     

Characterization of ADP-glucose pyrophosphorylase from shrunken-2 and brittle-2 mutants of maize

Electrophoretic characterization of adenosine diphosphate glucose pyrophosphorylase from the developing endosperms of nine shrunken-2 and four brittle-2 mutants revealed that (1) all mutants had low but detectable levels of activity, (2) mutation at either locus decreased activity of pyrophosphorylases A and B, and (3) differences in mobility were not found. However, pyrophosphorylase B extracted from several shrunken-2 and brittle-2 mutants differed from normal in extent of urea denaturation, K _m (glucose-1-phosphate) or type of glucose-1-phosphate saturation kinetics. Pyrophosphorylase B from sh2-m (association of Dissociation with the sh2 locus) appears to differ from normal in K _m (glucose-1-phosphate).This research was supported by the College of Agricultural and Life Sciences and by National Institutes of Health Grant No. 15422.The investigations reported were included in the thesis submitted by L. C. Hannah to the Graduate School, University of Wisconsin, Madison, Wisconsin, in partial fulfillment of requirement for the Ph.D. degree. Laboratory of Genetics Paper No. 1922.     

Lattice‐Matching Structurally‐Stable 1D@3D Perovskites toward Highly Efficient and Stable Solar Cells

The stability of perovskite solar cells (PSCs) has been identified to be the bottleneck toward their industrialization. With the aim of tackling this challenge, a 1D PbI₂‐bipyridine (BPy)(II) perovskite is fabricated, which is shown to be capable of in situ assembly of a 1D@3D perovskite that is promoted by a PbI₂‐dimethyl sulfoxide complex with a skeletal linear chain structure. The as‐prepared 1D@3D perovskite is observed to demonstrate extremely high stability under external large electric fields in humid environments by means of an in situ characterization technique. This stability is associated with its well lattice‐matching heterojunction structure between 1D and 3D heterojunction domains. Importantly, ion migration is alleviated through blocking of the ion‐migration channels. Accordingly, the 1D@3D hybrid PSC shows a power conversion efficiency of 21.18% maintaining remarkably high long‐term stability in the presence of water, illumination, and external electric fields. This rational design and microstructure study of 1D@3D perovskites provides a new paradigm that may enable higher efficiency and stability of PSCs.     

A functional abc for biotechnology and the dissemination of its progeny

In this paper we present a functional analysis of biotechnology and identify the particular status that genetic engineering has relative to other biotechnological techniques such as domestication. The analysis builds on work by Dan Sperber and characterises biotechnology in primarily technical and biological functional terms as symbiotic interactions in which humans modify other organisms. We identify three main routes by which these interactions are established in biotechnology. We argue that two of these routes have in-built mechanisms for preventing an uncontrolled dissemination of the modified organisms, and that one has an in-built mechanism for promoting such dissemination. The three routes are available to traditional forms of biotechnology as to state-of-the-art genetic engineering. Drawing now on work by Alfred Nordmann on the uncanniness of modern technologies, we show that genetic engineering is set apart by the epistemic consequences of the microscopic size of its progeny: genetically modified organisms, when disseminating, do so beyond our perceptual and conceptual control. Existing strategies against unwanted dissemination of organisms modified in traditional biotechnology are therefore typically not adequate against possible unwanted dissemination of genetically modified organisms, giving this dissemination a status similar to that of untraceable natural disasters.