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1.
2.
《Cell》2021,184(22):5670-5685.e23
3.
Biomass production and plant species diversity in grassland in southern England was monitored before and after a change from conventional to organic farming. Our 18-year study, part of the UK's Environmental Change Network long-term monitoring programme, showed that the cessation of artificial fertiliser use on grassland after conversion to organic farming resulted in a decrease in biomass production and an increase in plant species richness. Grassland productivity decreased immediately after fertiliser application ceased, and after two years the annual total biomass production had fallen by over 50%. In the subsequent decade, total annual grassland productivity did not change significantly, and yields reached 31–66% of the levels recorded pre-management change. Plant species richness that had remained stable during the first 5 years of our study under conventional farming, increased by 300% over the following 13 years under organic farm management. We suggest that the change in productivity is due to the altered composition of species within the plots. In the first few years after the change in farming practice, high yielding, nitrogen-loving plants were outcompeted by lower yielding grasses and forbs, and these species remained in the plots in the following years. This study shows that grassland can be converted from an environment lacking in plant species diversity to a relatively species-rich pasture within 10–15 years, simply by stopping or suspending nitrogen additions. We demonstrate that the trade-off for increasing species richness is a decrease in productivity. Grassland in the UK is often not only managed from a conservation perspective, but to also produce a profitable yield. By considering the species composition and encouraging specific beneficial species such as legumes, it may be possible to improve biomass productivity and reduce the trade-off. 相似文献
4.
Laran T. Jensen J. M. Peltier Dennis R. Winge 《Journal of biological inorganic chemistry》1998,3(6):627-631
Mammalian metallothioneins (MT) are known to maximally bind 12 copper ions in two six-Cu(I) ion clusters. Using electrospray
ionization mass spectrometry of MT at pH 4.5, a four-Cu(I) ion cluster was observed intermediate to a fully formed six Cu(I)
in a single domain or a fully formed Cu12MT species. The four-Cu(I) cluster was observed in both MT1 and MT3 isoforms. Addition of increasing amounts of Cu(I) to MT
at pH 4.5 resulted in prominent ions whoses masses were consistent with apo-MT, Cu4MT, Cu6MT, and Cu12MT. The cooperativity of cluster formation was reduced at pH 2.5. Addition of Cu(I) to apo-MT at a reduced pH resulted in
a series of ions consistent with Cu4 to Cu12MT species. However, formation of the tetracopper MT species remained cooperative at low pH, suggesting that this species
is very stable. To determine whether the tetracopper cluster was formed in either the α or β domain, domain peptides of MT3
were used. Addition of Cu(I) to the apo β domain resulted in a peak consistent with the formation of a four-Cu(I) cluster.
This is consistent with reports that Cu(I) ions bind preferentially to the β domain of MTs.
Received: 2 June 1998 / Accepted: 21 August 1998 相似文献
5.
The critical weed-free period in organically-grown winter wheat 总被引:1,自引:0,他引:1
J P WELSH H A J BULSON C E STOPES R J FROUD-WILLIAMS A J MURDOCH 《The Annals of applied biology》1999,134(3):315-320
Two experiments were conducted in central southern England between September 1994 and August 1996 to identify the critical weed-free period in organically grown winter wheat (Triticum aestivum, cv. Mercia). In competition with a mixed weed infestation of predominately Alopecurus myosuroides and Tripleurospermum inodorum it was found that wheat yield decreased as the duration of the weed-infested period increased and that the crop needed to be kept free of weeds from sowing in order to completely avoid any yield loss. Also, weeds emerging in the wheat crop (predominately T. inodorum) during the growing season had a significant and detrimental effect on yield. The existence of the critical period, therefore, depends on the imposition of an acceptable yield loss. If a 5% yield loss gives a marginal benefit compared with the cost of weed control, the critical period will begin at 506°C days after sowing (November) and end at 1023°C days after sowing (February). This information could be used by farmers to target mechanical weeding operations to control weeds at a time that will have maximum benefit to the crop. 相似文献
6.
Peter-Leon Hagedoorn Laura van der Weel Wilfred R. Hagen 《Journal of visualized experiments : JoVE》2014,(93)
Electron Paramagnetic Resonance (EPR) monitored redox titrations are a powerful method to determine the midpoint potential of cofactors in proteins and to identify and quantify the cofactors in their detectable redox state.The technique is complementary to direct electrochemistry (voltammetry) approaches, as it does not offer information on electron transfer rates, but does establish the identity and redox state of the cofactors in the protein under study. The technique is widely applicable to any protein containing an electron paramagnetic resonance (EPR) detectable cofactor.A typical titration requires 2 ml protein with a cofactor concentration in the range of 1-100 µM. The protein is titrated with a chemical reductant (sodium dithionite) or oxidant (potassium ferricyanide) in order to poise the sample at a certain potential. A platinum wire and a Ag/AgCl reference electrode are connected to a voltmeter to measure the potential of the protein solution. A set of 13 different redox mediators is used to equilibrate between the redox cofactors of the protein and the electrodes. Samples are drawn at different potentials and the Electron Paramagnetic Resonance spectra, characteristic for the different redox cofactors in the protein, are measured. The plot of the signal intensity versus the sample potential is analyzed using the Nernst equation in order to determine the midpoint potential of the cofactor. 相似文献
7.
8.
The literature pertaining to the use of registered antibacterial agents in Mediterranean finfish farming is reviewed, with
an emphasis on the Greek fish-farming industry. This review provides a scientific resource dedicated to the design of future
antibacterial dosing regimes in Mediterranean fish farming, where insufficient supporting information is currently available.
This paper addresses the paucity in knowledge concerning pharmacokinetics and the efficacy and environmental impact of commonly
used antibacterials needed to direct future research and promote good practices in the euryhaline fish farming industry. Several
registered antibacterials are currently available for combating bacterial infections, including tetracyclines, (fluoro) quinolones,
potentiated sulfa, penicillin and chloramphenicol derivatives. Based on the available data, oxytetracycline (OTC) and quinolone
drugs (oxolinic acid – OA and flumequine – FLU) are the most widely used in Mediterranean aquaculture. As a result these drugs
have received the most extensive studies, whereas, there is considerable paucity of reliable data on pharmacokinetic and the
depletion characteristics of other drugs used, particularly potentiated sulfa, penicillin derivatives and florfenicol. We
find there is incomplete data on drug efficacy and minimum inhibitory concentrations (MIC) for common antibacterials used
against the major bacterial pathogens of Mediterranean fish species. Furthermore, a considerable lack of data on environmental
drug concentrations around Mediterranean fish farms was also identified, highlighting the need for more extensive environmental
studies to monitor contamination in environmental components i.e., water and sediment, and in non-target species (flora and
fauna). Prudent selection and use of antibacterials can encourage lower dosage applications, enhance treatment efficacy, and
help to minimize contamination of the environment. Selection of readily bioavailable drugs which have low environmental persistence,
low aquatic toxicity and high antibacterial efficacy is advised, to reduce potential losses to the environment and associated
toxic effects on target species and the development of bacterial resistance. Lack of present data made it impossible to provide
thorough and accurate guidance on selection and use of antibacterials and approaches for minimizing environmental impacts
for the treatment of major euryhaline aquaculture species. 相似文献
9.
David J. Campbell 《Human ecology: an interdisciplinary journal》1984,12(1):35-64
From 1972 to 1976 rainfall in Kajiado District of Kenya was below normal. The capacity of the farming and herding systems to cope with the consequent reduction in production is discussed within a context of changing land-use patterns and altered resource availability. It is concluded that land-use planning to allocate the available land and water resources and to promote off-farm employment is required to reduce the vulnerability of the population to future drought conditions. 相似文献
10.
P. Huart R. Brasseur E. Goormaghtigh J.M. Ruysschaert 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,799(2):199-202
We demonstrate here that drugs which inactivate cytochrome c oxidase are able to segregate cardiolipin essential for the enzyme activity, in a separate phase inaccessible for the enzyme. A molecular explanation of the drug-induced aggregation process is proposed. 相似文献