Snow mould caused by a Pythium sp.: a potential vascular plant pathogen in the maritime Antarctic     

P. D. Bridge  K. K. Newsham  G. J. Denton 《Plant pathology》2008,57(6):1066-1072

The pathogenicity of an isolate of a Pythium species from Signy Island in the South Orkney Islands was tested against the Antarctic hairgrass Deschampsia antarctica. The isolate was found to infect plants at 8ºC and to cause foliar and root symptoms similar to those seen in other Pythium infections in grasses. Analysis of ribosomal RNA sequences placed it, together with another isolate from Antarctica, in a clade that included the known snow moulds caused by Pythium spp. Sporangia and oogonia were produced in culture, but the isolate differed from other Pythium spp. in producing chlamydospores in older cultures and plant tissue. This is the first report of a pathogen of an eukaryotic vascular plant in the maritime Antarctic region.  相似文献   

Modelling primary branch frequency and size for five conifer species in Maine,USA   总被引：1，自引：0，他引：1  

Aaron R. Weiskittel  Robert S. Seymour  Philip V. Hofmeyer  John A. Kershaw Jr. 《Forest Ecology and Management》2010

Quantitative models of crown structure have been developed for several conifer species, but these studies have rarely simultaneously fit the models across multiple species. This study used extensive crown structure data for the five primary conifer species in Maine to test for species differences in maximum branch diameter profile, branch density, and relative branch diameter distribution. The species included balsam fir [Abies balsamea (L.) Mill], northern white-cedar [Thuja occidentalis (L.)], eastern hemlock [Tsuga canadensis (L.) Carr.], eastern white pine [Pinus strobus (L.)], and red spruce [Picea rubens (Sarg.)]. After accounting for key covariates, significant species differences were found in all crown structural attributes examined in this study. Profiles for the mean tree indicated that northern white-cedar had the smallest maximum branch diameters throughout the crown and white pine had the largest, except near the base of the crown where the species switched in rank. The density of live branches in a crown had the widest range of variation of the examined crown structural attributes. Red spruce had a significantly higher density of primary branches than the other conifers, particularly in the upper crown. The relative branch diameter distribution indicated that balsam fir had a distribution more skewed towards larger relative branch sizes, while eastern hemlock and red spruce had distributions shifted towards smaller relative branches. This study highlights the range of variability in key crown structural attributes due to inherent species differences, but indicates that models fit across multiple species can perform quite well as the amount of explained variation was relatively high.  相似文献   

THE EFFECT OF FORMALDEHYDE UPON THE VITAMIN CONTENT OF MILK     

Bleile AM  Seymour RJ 《Science (New York, N.Y.)》1923,58(1512):518-520

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Estimation of Root-knot Nematode Infestation Levels on Roots Using a Rating Chart   总被引：2，自引：0，他引：2  

J. Bridge  S. L. J. Page 《国际虫害防治杂志》2013,59(3):296-298

Abstract

A rating chart is given which enables easy and accurate field assessment of damage by root-knot nematodes (Meloidogyne spp.) on many crops, based on the percentage and types of roots galled. It should be of use both to nematologists and untrained field workers.  相似文献   

Spatio-temporal patterns of pre-harvest brown rot epidemics within individual peach tree canopies     

S. E. Everhart  A. Askew  L. Seymour  H. Scherm 《European journal of plant pathology / European Foundation for Plant Pathology》2013,135(3):499-508

Tree canopies are architecturally complex and pose several challenges for measuring and characterizing spatial patterns of disease. Recently developed methods for fine-scale canopy mapping and three-dimensional spatial pattern analysis were applied in a 3-year study to characterize spatio-temporal development of pre-harvest brown rot of peach, caused by Monilinia fructicola, in 13 trees of different maturity classes. We observed a negative correlation between an index of disease aggregation and disease incidence in the same tree (r?=??0.653, P?<?0.0001), showing that trees with higher brown rot incidence had lower aggregation of affected fruit in their canopies. Significant (P?≤?0.05) within-canopy aggregation among symptomatic fruit was most pronounced for early-maturing cultivars and/or early in the epidemic. This is consistent with the notion of a greater importance of localized, within-tree sources of inoculum at the beginning of the epidemic. Four of five trees having >10 blossom blight symptoms per tree showed a significant positive spatial association of pre-harvest fruit rot to blossom blight within the same canopy. Spatial association analyses further revealed one of two outcomes for the association of new fruit rot symptoms with previous fruit rot symptoms in the same tree, whereby the relationship was either not significant or exhibited a significant negative association. In the latter scenario, the newly diseased fruit were farther apart from previously symptomatic fruit than expected by random chance. This unexpected result could have been due to uneven fruit ripening in different sectors of the canopy, which could have affected the timing of symptom development and thus led to negative spatial associations among symptoms developing over time in a tree.  相似文献   

Dietary exposure of Canadians to perfluorinated carboxylates and perfluorooctane sulfonate via consumption of meat, fish, fast foods, and food items prepared in their packaging   总被引：2，自引：0，他引：2  

Tittlemier SA  Pepper K  Seymour C  Moisey J  Bronson R  Cao XL  Dabeka RW 《Journal of agricultural and food chemistry》2007,55(8):3203-3210

Human exposure to perfluorinated compounds is a worldwide phenomenon; however, routes of human exposure to these compounds have not been well-characterized. Fifty-four solid food composite samples collected as part of the Canadian Total Diet Study (TDS) were analyzed for perfluorocarboxylates and perfluorooctanesulfonate (PFOS) using a methanol extraction liquid chromatography tandem mass spectrometry method. Foods analyzed included fish and seafood, meat, poultry, frozen entrées, fast food, and microwave popcorn collected from 1992 to 2004 and prepared as for consumption. Nine composites contained detectable levels of perfluorinated compounds-four meat-containing, three fish and shellfish, one fast food, and one microwave popcorn. PFOS and perfluorooctanoate (PFOA) were detected the most frequently; concentrations ranged from 0.5 to 4.5 ng/g. The average dietary intake of total perfluorocarboxylates and PFOS for Canadians was estimated to be 250 ng/day, using results from the 2004 TDS composites. A comparison with intakes of perfluorocarboxylates and PFOS via other routes (air, water, dust, treated carpeting, and apparel) suggested that diet is an important source of these compounds. There was a substantial margin of exposure between the toxicological points of reference and the magnitude of dietary intake of perfluorinated compounds for Canadians >/= 12 years old.  相似文献   

Influence of atmospheric deposition on lake mass balances in the Turkey Lakes Watershed,Central Ontario     

D. S. Jeffries  R. G. Semkin  R. Neureuther  M. Seymour  J. A. Nicolson 《Water, air, and soil pollution》1986,30(3-4):1033-1044

Ion mass budgets were measured for 2 water yr (June–May, 1981–83) for a high and a ).ow elevation lake and their associated catchments. The lakes are located in the Turkey Lakes Watershed (TLW) in central Ontario, Canada, which is an undeveloped basin located on the Canadian Shield, 50 km north of Sault Ste. Marie. The ionic budgets of the lakes show that atmospheric deposition directly to the lakes' surfaces is the principal input pathway for H⁺ and NH₄, whereas basic cations, SO₄, NO₃, and probably alkalinity are supplied primarily by inflow from the surrounding terrestrial basin and/or upstream lake. The lakes strongly retain H⁺ (i.e. output ? input), weakly retain the N species, and are in balance (i.e. output = input) for other ions except Ca and alkalinity which show an excess output compared to measured + estimated inputs. We hypothesize that an input of groundwater and/or seepage accounts for most of the Ca and alkalinity imbalance although the existence of within-lake alkalinity generation is probable also.  相似文献   

Ethical question of the month — November 2002          下载免费PDF全文

Kathy Zurbrigg  Ken Bridge 《The Canadian veterinary journal. La revue veterinaire canadienne》2002,43(11):828

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A potentially fatal complication of arterial cannulation caused by a faulty T-connector     

Robinson R  Seymour C 《Veterinary anaesthesia and analgesia》2011,38(3):274-275

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Plasma observations near uranus: initial results from voyager 2     

Bridge HS  Belcher JW  Coppi B  Lazarus AJ  McNutt RL  Olbert S  Richardson JD  Sands MR  Selesnick RS  Sullivan JD  Hartle RE  Ogilvie KW  Sittler EC  Bagenal F  Wolff RS  Vasyliunas VM  Siscoe GL  Goertz CK  Eviatar A 《Science (New York, N.Y.)》1986,233(4759):89-93

Extensive measurements of low-energy positive ions and electrons in the vicinity of Uranus have revealed a fully developed magnetosphere. The magnetospheric plasma has a warm component with a temperature of 4 to 50 electron volts and a peak density of roughly 2 protons per cubic centimeter, and a hot component, with a temperature of a few kiloelectron volts and a peak density of roughly 0.1 proton per cubic centimeter. The warm component is observed both inside and outside of L = 5, whereas the hot component is excluded from the region inside of that L shell. Possible sources of the plasma in the magnetosphere are the extended hydrogen corona, the solar wind, and the ionosphere. The Uranian moons do not appear to be a significant plasma source. The boundary of the hot plasma component at L = 5 may be associated either with Miranda or with the inner limit of a deeply penetrating, solar wind-driven magnetospheric convection system. The Voyager 2 spacecraft repeatedly encountered the plasma sheet in the magnetotail at locations that are consistent with a geometric model for the plasma sheet similar to that at Earth.  相似文献