杂交水稻的根呼吸--四种耗氧途径的活力和P/O比     

石庆华  Ries de Visser 《江西农业大学学报》2000,22(3):313-316

对杂交水稻赣化７号和其亲本之一广抗粳２号的根系耗氧特征进行了研究,稻株种植在通气的营养液中,４种耗氧途径的活力被量化分析。过氧化物酶耗氧占了较大的比例,龙胆酸可抑制稻根中的过氧化物酶活力。杂交水稻的过氧化物酶和抗氰酸呼吸途径耗氧率比其亲本高５０％以上,杂交水稻和其亲本根系过氧化物酶的耗氧分别占总量的２６．５％和２２．６％,细胞色素氧化酶途径分别占３５．５％和４０．５％,抗氰酸呼吸途径分别占２７．８  相似文献   

Perception and acceptance of agricultural production in and on urban buildings (ZFarming): a qualitative study from Berlin,Germany     

Kathrin Specht  Rosemarie Siebert  Susanne Thomaier 《Agriculture and Human Values》2016,33(4):753-769

Rooftop gardens, rooftop greenhouses and indoor farms (defined as ZFarming) have been established or planned by activists and private companies in Berlin. These projects promise to produce a range of goods that could have positive impacts on the urban setting but also carry a number of risks and uncertainties. In this early innovation phase, the relevant stakeholders’ perceptions and social acceptance of ZFarming represent important preconditions for success or failure of the further diffusion of this practice. We used the framework of acceptance to investigate the stakeholders’ attitudes and to identify the key factors that might hinder or promote the introduction of ZFarming. The results are based on an analysis of 38 qualitative interviews conducted with key stakeholders in Berlin. As the results show, major perceived benefits of ZFarming include improved consumer awareness, education, and the creation of experimental spaces. Stakeholders further perceive opportunities for resource savings, new business models, repurposing of abandoned buildings and improved aesthetics. Major perceived risks are associated with growing techniques that are considered “unnatural”, health risks (due to urban pollutants), conflicts with images of traditional agriculture, the rejection of animal production in urban areas, the risk of projects being too expensive and too complex or being implemented too early, i.e. before the mechanisms are fully understood. The analysis further reveals which contextual factors—political, legal, market-related, spatial or societal—might negatively or positively influence ZFarming acceptance.  相似文献   

Long-Term Complications of Rattlesnake Bites: A Telephone Survey From Central California     

Susanne J. Spano  Rais Vohra  Fernando Macias 《The Forestry Chronicle》2014,25(2):210-213

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Species-specific responses to environmental stress on germination and juvenile growth of two Bolivian Andean agroforestry species     

Regine Brandt  Susanne Lachmuth  Catharina Landschulz  Friedemann Haß  Isabell Hensen 《New Forests》2014,45(6):777-795

Integrating native trees in farmland can support soil, water and biodiversity conservation. This is particularly important in regions characterized by long periods of drought and soil erosion, such as the Bolivian Andes, where agroforestry with native woody species is rarely applied. Better knowledge on the effects of environmental stress on propagation and establishment of such native plants is needed to optimize their cultivation. In our study, we tested the effects of temperature and scarification on seed germination, and assessed seedling survival and juvenile growth of two potential agroforestry species (Prosopis laevigata var. andicola, Schinus molle) under diverse soil and water conditions. Temperatures above 30 °C accelerated germination, but they increased fungi infestation in the case of S. molle. The application of acid and mechanical scarification significantly improved the germination capacity of P. laevigata var. andicola. Medium to high moisture levels in sand provided the most favourable conditions for plant growth. S. molle was more sensitive to dry and P. laevigata var. andicola more vulnerable to water-saturated clay loam. Mulching enhanced the survival and growth of S. molle juveniles, but increased P. laevigata var. andicola’s growth in sand and dry soils only. Our results may facilitate guidance on improving propagation of these two potential agroforestry species under environmental stress conditions. More generally, our study shows that easily applicable treatments, such as mulching, can significantly improve the cultivation of native species, provided that their habitat requirements and limiting factors are well known. This highlights the relevance of identifying and closing such knowledge gaps for native trees and shrubs in order to promote their potential for use in agroforestry.  相似文献   

Flocculation mechanism: charge neutralization and bridging     

Ries HE  Meyers BL 《Science (New York, N.Y.)》1968,160(3835):1449-1450

Electrophoresis measurements and electron-microscope observations with two model colloids and a polymeric flocculant show zeta-potential changes and details of floc structure. Fibers of the flocculant extend radially from the particle surface and vary in thickness from 20 to 300 angstroms. Both charge neutralization and bridging may function simultaneously.  相似文献   

Tryptophan 7-halogenase (PrnA) structure suggests a mechanism for regioselective chlorination     

Dong C  Flecks S  Unversucht S  Haupt C  van Pée KH  Naismith JH 《Science (New York, N.Y.)》2005,309(5744):2216-2219

Chlorinated natural products include vancomycin and cryptophycin A. Their biosynthesis involves regioselective chlorination by flavin-dependent halogenases. We report the structural characterization of tryptophan 7-halogenase (PrnA), which regioselectively chlorinates tryptophan. Tryptophan and flavin adenine dinucleotide (FAD) are separated by a 10 angstrom-long tunnel and bound by distinct enzyme modules. The FAD module is conserved in halogenases and is related to flavin-dependent monooxygenases. On the basis of biochemical studies, crystal structures, and by analogy with monooxygenases, we predict that FADH2 reacts with O2 to make peroxyflavin, which is decomposed by Cl-. The resulting HOCl is guided through the tunnel to tryptophan, where it is activated to participate in electrophilic aromatic substitution.  相似文献   

COX-2-derived prostacyclin confers atheroprotection on female mice   总被引：1，自引：0，他引：1  

Egan KM  Lawson JA  Fries S  Koller B  Rader DJ  Smyth EM  Fitzgerald GA 《Science (New York, N.Y.)》2004,306(5703):1954-1957

Female gender affords relative protection from cardiovascular disease until the menopause. We report that estrogen acts on estrogen receptor subtype alpha to up-regulate the production of atheroprotective prostacyclin, PGI2, by activation of cyclooxygenase 2 (COX-2). This mechanism restrained both oxidant stress and platelet activation that contribute to atherogenesis in female mice. Deletion of the PGI2 receptor removed the atheroprotective effect of estrogen in ovariectomized female mice. This suggests that chronic treatment of patients with selective inhibitors of COX-2 could undermine protection from cardiovascular disease in premenopausal females.  相似文献   

Large-scale copy number polymorphism in the human genome   总被引：1，自引：0，他引：1  

Sebat J  Lakshmi B  Troge J  Alexander J  Young J  Lundin P  Månér S  Massa H  Walker M  Chi M  Navin N  Lucito R  Healy J  Hicks J  Ye K  Reiner A  Gilliam TC  Trask B  Patterson N  Zetterberg A  Wigler M 《Science (New York, N.Y.)》2004,305(5683):525-528

The extent to which large duplications and deletions contribute to human genetic variation and diversity is unknown. Here, we show that large-scale copy number polymorphisms (CNPs) (about 100 kilobases and greater) contribute substantially to genomic variation between normal humans. Representational oligonucleotide microarray analysis of 20 individuals revealed a total of 221 copy number differences representing 76 unique CNPs. On average, individuals differed by 11 CNPs, and the average length of a CNP interval was 465 kilobases. We observed copy number variation of 70 different genes within CNP intervals, including genes involved in neurological function, regulation of cell growth, regulation of metabolism, and several genes known to be associated with disease.  相似文献   

DNA: a programmable force sensor     

Albrecht C  Blank K  Lalic-Mülthaler M  Hirler S  Mai T  Gilbert I  Schiffmann S  Bayer T  Clausen-Schaumann H  Gaub HE 《Science (New York, N.Y.)》2003,301(5631):367-370

Direct quantification of biomolecular interaction by single-molecule force spectroscopy has evolved into a powerful tool for materials and life sciences. We introduce an approach in which the unbinding forces required to break intermolecular bonds are measured in a differential format by comparison with a known reference bond (here, a short DNA duplex). In addition to a marked increase in sensitivity and force resolution, which enabled us to resolve single-base pair mismatches, this concept allows for highly specific parallel assays. This option was exploited to overcome cross-reactions of antibodies in a protein biochip application.  相似文献   

Efficient inhibition of the Alzheimer's disease beta-secretase by membrane targeting     

Rajendran L  Schneider A  Schlechtingen G  Weidlich S  Ries J  Braxmeier T  Schwille P  Schulz JB  Schroeder C  Simons M  Jennings G  Knölker HJ  Simons K 《Science (New York, N.Y.)》2008,320(5875):520-523

beta-Secretase plays a critical role in beta-amyloid formation and thus provides a therapeutic target for Alzheimer's disease. Inhibitor design has usually focused on active-site binding, neglecting the subcellular localization of active enzyme. We have addressed this issue by synthesizing a membrane-anchored version of a beta-secretase transition-state inhibitor by linking it to a sterol moiety. Thus, we targeted the inhibitor to active beta-secretase found in endosomes and also reduced the dimensionality of the inhibitor, increasing its local membrane concentration. This inhibitor reduced enzyme activity much more efficiently than did the free inhibitor in cultured cells and in vivo. In addition to effectively targeting beta-secretase, this strategy could also be used in designing potent drugs against other membrane protein targets.  相似文献