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M. WOODBINE E. B. REID EILEEN M. C. SCORER AUDREY A. GRANT CONSTANCE M. McKAY 《Journal of applied microbiology》1953,16(1):56-61
SUMMARY: A process for dehydrating fish under vacuum and in contact with heated plates is described. Although the conditions, in respect of time and temperature, appeared suitable for microbial development, a reduction in the number of bacteria usually occurred. A survey of the data accumulated over twenty months, including a series of experimental production periods, showed that the bacterial population estimated at 22° was reduced in the process as a whole to about 1% of its initial value and that estimated at 37° to about 10%. Species of the genus Micrococcus tended to predominate on the finished product. Contrary to earlier expectations, there should be no serious microbiological hazards if high standards of personal and factory hygiene are maintained. 相似文献
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A fossil carabid (Coleoptera) belonging to the subfamily Promecognathinae is described from Cretaceous crater lake deposits at Orapa, Botswana. The specimen, which is the first ever fossil promecognathine, is placed in a new genus Palaeoxinidium. The fossil supports a Cretaceous age determination for the sediments, and it indicates that the Orapa crater was, at least in part, heavily vegetated at the time of deposition. Cladistic analysis of the fossil and extant Promecognathinae indicates that the fossil represents the sister group of the extant taxa and that the latter, in turn, comprise a pair of sister groups. It is, therefore, proposed that the Promecognathinae should be divided into two tribes: the Palaeoaxinidiini, represented by the fossil, and the Promecognathini, represented by the extant groups. The Promecognathini should be subdivided further into the subtribes Promecognathina and Axinidiina, represented by the American and African species, respectively. Three alternative zoogeographic hypotheses that explain the distributions of the fossil and extant promecognathines are discussed and tests for the hypotheses are proposed. 相似文献
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The form of fine roots of Sitka spruce (Picea sitchensis Bong.Carr.) when grown in immediate proximity to roots of Scots pine(Pinus sylvestris L.) and when grown separately was comparedusing split-root systems. When spruce roots were intimatelymixed with pine roots the mean length of individual spruce lateralswas significantly greater, while the length: weight ratio andnumber of root tips: weight ratio were smaller than when grownalone. A similar alteration in growth strategy was achievedby direct addition of mineral nitrogen. Key words: Fine root form, pine-spruce interactions 相似文献
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R. M. L. McKAY † G. R. PALMER X. P. MA D. B. LAYZELL B. T. A. McKEE 《Plant, cell & environment》1988,11(9):851-861
Abstract. Positron emission tomography (PET) has been utilized to obtain dynamic images of long distance nutrient translocation in plants. Positron emitting 18 F, produced by a Van de Graaff accelerator using the reaction 18 O(p,n)18 F, was fed in solution to excised stems of Glycine max positioned vertically in a large-aperture PET detector system. Images of tracer activity were recorded with a time resolution of 0.5 min and a spatial resolution of 4 mm. Maximum tracer activities at stem sites were obtained within 3 min of the pulse feed. A model is presented enabling evaluation of regional values for tracer flow, tracer binding, flow speed and flow volume. Analysis of data for one stem position yielded a flow volume of 2.1mm3 min−1 and a flow speed of 36cm min−1 . Comparison with the distribution of 14 C-inulin, which was simultaneously fed to the cut stems, indicates the 18 F is suitable for use as an apoplastic tracer; 92% of the tracer activity accumulated in the leaves. The fraction of 18 F that remained bound was most concentrated at stem nodal regions, an observation consistent with the existence of transfer cells at these sites. Advantages and limitations of PET applied to plant physiological investigations are discussed. 相似文献
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Sixteen 1-ha study plots covering five regeneration stages were simultaneously trapped five times over a 20-month period to provide data on small mammal response to vegetation changes following fire. Areas regenerating after fires from 9 years to 1 month before the investigation were sampled in a uniform open forest on a coastal sand plain. Two types of understorey were recognized: one dominated by true forest shrubs with which Rattus fuscipes, Antechinus stuartii and Sminthopsis murina were associated, and another dominated by heath elements where the addition of Pseudomys novaehollandiae and Mus musculus produced a significantly more diverse small mammal community. The two communities exhibited different responses to post-fire vegetation changes. Rattus fuscipes was the most abundant species and showed a logistic growth in biomass. No resident populations were established in the first 3 years, but a rapid increase in biomass occurred from 3 to 5 years to plateau after 8 years. Regeneration age had the greatest effect on R. fuscipes biomass mediated through the amount of accumulated leaf litter with additional variation being attributed to several vegetation structure variables and plant species diversity. A replacement sequence in time was observed for species reaching their maximum abundance (P. novaehollandiae and/or M. musculus → S. murina → A. stuartii → R. fuscipes) and was interpreted as species occupying stages in the succession when their optimal habitat requirements were fulfilled. These results have important implications for the design of management policies using fire or fire regimes as tools for habitat maintenance or alteration. A mosaic of forest patches of adequate size covering the entire range of seral stages is necessary to meet the optimum requirements of all the above species. 相似文献
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JESSE R. LASKY DAVID L. DES MARAIS JOHN K. McKAY JAMES H. RICHARDS THOMAS E. JUENGER TIMOTHY H. KEITT 《Molecular ecology》2012,21(22):5512-5529
Arabidopsis thaliana inhabits diverse climates and exhibits varied phenology across its range. Although A. thaliana is an extremely well‐studied model species, the relationship between geography, growing season climate and its genetic variation is poorly characterized. We used redundancy analysis (RDA) to quantify the association of genomic variation [214 051 single nucleotide polymorphisms (SNPs)] with geography and climate among 1003 accessions collected from 447 locations in Eurasia. We identified climate variables most correlated with genomic variation, which may be important selective gradients related to local adaptation across the species range. Climate variation among sites of origin explained slightly more genomic variation than geographical distance. Large‐scale spatial gradients and early spring temperatures explained the most genomic variation, while growing season and summer conditions explained the most after controlling for spatial structure. SNP variation in Scandinavia showed the greatest climate structure among regions, possibly because of relatively consistent phenology and life history of populations in this region. Climate variation explained more variation among nonsynonymous SNPs than expected by chance, suggesting that much of the climatic structure of SNP correlations is due to changes in coding sequence that may underlie local adaptation. 相似文献
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