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51.
52.
The Amsterdam albatross (Diomedea amsterdamensis) is one of the rarest bird species of world avifauna, consisting of a single population in the upland plateau of Amsterdam Island (SE Indian Ocean). All breeding birds of the population are today banded and a monitoring program involving mark-recapture procedures has been carried out continuously over the past 16 years. We present the first estimate of risk of decline for the Amsterdam albatross using a stochastic matrix population model, and evaluate the extent to which the measurement errors in demographic estimates may affect the baseline conservation assessment. We also estimate the potential effect that resumption of long-line fisheries in the vicinity of Amsterdam Island (one the alleged causes for its low numbers in the recent past) may have on the persistence of this population. Our results indicate that, in the absence of any impact of long-line fisheries, the Amsterdam albatross is unlikely to experience a decline larger than 20% of the current population abundance over the next 50 years. Our results point out the difficulty to assess with certainty the extinction risk of small populations despite the availability of long term data on their demography. They suggest that a very cautious approach should be taken for the preservation of small populations of long-lived species that cannot sustain any level of incidental by-catch. Any new long-line fishery resuming in the foraging range of the Amsterdam albatross, but especially close to Amsterdam Island, may rapidly put this species at risk of extinction. 相似文献
53.
54.
Anther culture is a convenient technique to obtain androgenic haploid and doubled haploid (DH) plants. In common eggplant
(Solanum melongena), this technique has been used to develop DH pure lines for producing uniform F1 hybrid seed of some commercial varieties.
However, a comprehensive study of the variation of this useful trait among different materials of common eggplant and related
species is still lacking. In this work, we studied the androgenic response of 12 accessions of common eggplant and related
materials from the primary (eggplant complex) and secondary genepools. We cultured anthers of all the accessions under the
same experimental conditions, and studied their competence to produce calli, embryos and plants, as well as the quality and
origin of the embryos produced. In our conditions, anthers of 11 out of the 12 accessions produced somatic calli, whereas
only 5 also produced microspore-derived embryos, with variable results in terms of embryo quality and of frequency of embryo
induction and plant germination. Embryos of responding accessions were initially haploid, and reached the DH status, verified
with SSR markers, after a defined period of culture. In addition to other aspects common to many androgenesis-responsive species,
our results allowed us to extract conclusions particular to common eggplant and relatives, including the difficulty for finding
sources of androgenic competence out of S. melongena, the reduced impact of calli in the production of non-DH individuals, and the need to avoid the occurrence of severe anatomical
and functional problems in the apex of most embryos, which seriously reduces their germinative success. 相似文献
55.
The Penman–Monteith equation for reference evapotranspiration (ETo) estimation cannot be applied in many situations, because climatic records are totally or partially not available or reliable.
In these cases, empirical equations that rely on few climatic variables are necessary. Nevertheless, the uncertainty associated
with empirical model estimations is often high. Thus, the improvement of methods relying on few climatic inputs as well as
the development of emergency estimation tools that demand no local climatic records turns into a task of great relevance.
The present study describes different approaches based on multiple linear regression, simple regression and artificial neural
networks (ANNs) to deal with ETo estimation exclusively from exogenous records from secondary stations. This cross-station approach is based on a continental
characterization of the study region, which enables the selection and hierarchization of the most suitable ancillary data
supplier stations. This procedure is compared with different traditional and cross-station approaches, including methodologies
that also consider local temperature inputs. The proposed methods are also evaluated as gap infilling procedures and compared
with a simple methodology, the window averaging. The artificial neural network and the multiple linear regression approaches
present very similar performance accuracies, considerably higher than simple regression and traditional temperature-based
approaches. The proposed input combinations allow similar performance accuracies as ANN models relying on exogenous ETo records and local temperature measurements. The cross-station multiple linear regression procedure is recommended due to
its higher simplicity. 相似文献
56.
57.
Jadzinsky PD Calero G Ackerson CJ Bushnell DA Kornberg RD 《Science (New York, N.Y.)》2007,318(5849):430-433
Structural information on nanometer-sized gold particles has been limited, due in part to the problem of preparing homogeneous material. Here we report the crystallization and x-ray structure determination of a p-mercaptobenzoic acid (p-MBA)-protected gold nanoparticle, which comprises 102 gold atoms and 44 p-MBAs. The central gold atoms are packed in a Marks decahedron, surrounded by additional layers of gold atoms in unanticipated geometries. The p-MBAs interact not only with the gold but also with one another, forming a rigid surface layer. The particles are chiral, with the two enantiomers alternating in the crystal lattice. The discrete nature of the particle may be explained by the closing of a 58-electron shell. 相似文献
58.
Ferguson SM Brasnjo G Hayashi M Wölfel M Collesi C Giovedi S Raimondi A Gong LW Ariel P Paradise S O'toole E Flavell R Cremona O Miesenböck G Ryan TA De Camilli P 《Science (New York, N.Y.)》2007,316(5824):570-574
Dynamin 1 is a neuron-specific guanosine triphosphatase thought to be critically required for the fission reaction of synaptic vesicle endocytosis. Unexpectedly, mice lacking dynamin 1 were able to form functional synapses, even though their postnatal viability was limited. However, during spontaneous network activity, branched, tubular plasma membrane invaginations accumulated, capped by clathrin-coated pits, in synapses of dynamin 1-knockout mice. Synaptic vesicle endocytosis was severely impaired during strong exogenous stimulation but resumed efficiently when the stimulus was terminated. Thus, dynamin 1-independent mechanisms can support limited synaptic vesicle endocytosis, but dynamin 1 is needed during high levels of neuronal activity. 相似文献
59.
Paula Aguilera Fernando Borie Alex Seguel Pablo Cornejo 《Soil biology & biochemistry》2011,43(12):2427-2431
Arbuscular mycorrhizal spores and glomalin-related soil protein (GRSP) isolated from acid soils were analyzed using confocal laser scanning microscopy (CLSM) for Al detection. Mycorrhizal structures of Glomus intraradices produced under in vitro conditions as well as spores and GRSP from neutral and Cu-polluted soils were used as contrasting criteria. Spores and GRSP from soils with 7 and 70% Al saturation showed autofluorescence which increased especially at the highest soil Al level and when Al3+ solution was added. G.intraradices spores showed fluorescence only when exogenous Al3+ was added. On the contrary, spores and GRSP from neutral and Cu-polluted soils showed little or no significant fluorescence. This fluorescence shown by fungal structures and GRSP when subjected to high Al (of endogenous or exogenous origin) suggest a high capacity for Al immobilization, which could be an effective way to reduce Al activity and phytotoxicity in acid soils. 相似文献
60.
Adrien Gallou Hernán Patricio Lucero Mosquera Sylvie Cranenbrouck Juan Pablo Suárez Stéphane Declerck 《Physiological and Molecular Plant Pathology》2011,76(1):20-26
Biological control of soil-borne pathogens by arbuscular mycorrhizal (AM) fungi has been repeatedly demonstrated. However, their role in the control of above-ground hemibiotrophic pathogens is less conclusive. Here, we investigated in vitro the impact of an AM fungus on Phytophthora infestans in potato plants. The leaf infection index was decreased in mycorrhizal potato plants. Real-Time Quantitative PCR revealed the induction of two pathogenesis related genes (PR1 and PR2) in the leaves of mycorrhizal plants shortly after infection with P. infestans. These results suggested a systemic resistance in mycorrhizal plants, related to the priming of the two PR genes in potato. 相似文献