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161.
Identification of the main correlates of the invasion process is a fundamental step in alien species management at the regional scale. This paper explores the main climatic, territorial, and anthropic correlates of alien plant species richness and percentage in Catalonia (NE of Spain), by means of GIS techniques. We used floristic data collected in FLORACAT per UTM 10 km × 10 km to set up the number and the percentage of alien species. The association of these variables with climate, topography, landscape, human settlement, and geographic position was explored by means of stepwise regression models applied on the axes obtained from principal component analysis. The significance of the resulting correlates was tested using the modified t test of Dutilleul to remove the effects of spatial autocorrelation. PCA reduced the 22 variables to 12 principal components (PC) that explained 90% of the cumulative variance. Regression models were highly significant and captured a high proportion of total variance (adjusted r2 = 0.70 for alien species richness and r2 = 0.56 for alien species percentage). Both alien species richness and percentage were mainly correlated to PC summarising variables concerning climate, habitat and landscape heterogeneity, and potential anthropogenic disturbance. However, while these PC exhibited similar weights on alien species richness, species percentage was mainly determined by climate. Implications for conservation are discussed considering a future scenario of climate warming and increasing land use change in Mediterranean areas. 相似文献
162.
Five different cranberry (Vaccinium macrocarpon Ait.) cultivars were fertilized with either 0, 22, or 44 kg N ha/yr. After three consecutive years of these treatments, plant tissue samples were taken and analyzed for the elements, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), boron (B), iron (Fe), copper (Cu), and zinc (Zn). These were compared to N dose and to fruit quality and quantity parameters. Across all cultivars, tissue N, P, and K levels increased with increasing N dose, whereas Fe tended to decrease with increasing N dose. Only the element Mn showed no relationship to N dose for any cultivar. Tissue N concentration was generally unrelated to fruit yield. However, fruit rot (both field and storage) was strongly related to tissue N. Average berry weight was related to the tissue concentration of a number of elements. This research suggests that tissue nutrient concentration may be useful in predicting rot and fruit size potential in cranberries. 相似文献
163.
An indirect enzyme-linked immunoassay for serological surveillance of infection of pigs with Actinobacillus pleuropneumoniae (Ap) serotype 5 was developed. The antigen used was prepared from Ap serotype 5b strain L20. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the antigen contained high molecular weight lipopolysaccharide (LPS) and presumably also capsular polysaccharide (CP). The Ap serotype 5 ELISA was tested using sera from pigs experimentally infected with the 12 different Ap serotypes of biotype 1 and with sera from herds naturally infected with Ap serotypes 5, 6, 7 and 12. Cross-reactions were shown in one pig from a herd naturally infected with Ap serotype 7 and in one pig from a herd naturally infected with Ap serotype 12. The herd sensitivities of the Ap5 ELISA and a complement fixation test (CFT) were both estimated to 1.0, on the basis of serum samples from six herds naturally infected with Ap serotype 5. The herd specificities of both tests were estimated to 0.98, based on serum samples from 123 pig herds (10 samples from each herd) from the Danish specific pathogen-free (SPF) programme for pig production. 相似文献
164.
Extract The purpose of this paper is to describe the salient features of the neurological conditions seen in sheep in New Zealand which are associated with changes in the central nervous system. Several of the conditions associated with perinatal mortality will be mentioned only briefly in this paper as the details will be included in a subsequent paper on ovine perinatal mortality. Some of the entities to be described have been reported before and are reviewed. Others are described here for the first time. 相似文献
165.
Joan Hearman A. Beryl Beakbane R. G. Hatton W. A. Roach 《The Journal of Horticultural Science and Biotechnology》2013,88(4):376-390
SummaryThe purpose of this research was to determine if established, orchard-grown apple trees that were con®ned in root-restricting membranes received adequate water for growth when irrigated. Previous data had shown positive effects of root restriction on reducing shoot extension growth in apple. Soil matric potential (Ψsm), leaf stomatal conductance (g) and leaf water potentials (Ψl) were measured over daily cycles during the period of maximum tree water use (July and August). Measurements were also made of the Ψsm and fruit size throughout the growing season. Daily and seasonal Ψsm showed that the soil within the root restricting membranes (+R) when irrigated (+I) remained closed to field capacity (<100 HPa), which was not the case for unirrigated soil within the membranes (-I +R). Ψl measured before dawn, showed that similar levels of drought stress were evident between irrigated and restricted (+I +R) and unrestricted (+I -R and -I -R) trees. The Ψsm, and Ψl for trees with roots within restricting membranes were significantly more negative, in the absence of irrigation (-I +R). Measurement of g showed that root restricted trees were transpiring at similar rates in the presence of irrigation (+I +R) as unrestricted trees (+I -R) with or without irrigation. Stomatal closure could not explain the increased Ψl observed for the restricted irrigated (+I +R) treatment compared with unrestricted (-R) trees. A reduced stomatal aperture was the most likely explanation for the reduction in growth previously observed with the restricted unirrigated trees. Fruit size was also affected by root restriction and the effect became greater as the roots became more restricted with tree age. Similarly, there was also a negative effect, in one year, of root restriction on fruit size at harvest, even in the presence of irrigation. Data show that reductions in soil water availability, Ψl and g, for the root-restricted trees (+I +R), were unlikely to be the causes for the previously observed reductions in shoot growth (tree size). These results imply that other factors were in operation, among which root-synthesized chemical regulators of shoot growth are the most likely candidates. 相似文献
166.
Trudy J. Estes Joan U. Clarke Christian J. McGrath 《Journal of Soils and Sediments》2012,12(4):636-651
Purpose
Confined disposal facilities (CDFs) are widely used for disposal of navigation dredged material, but many are running out of capacity. Removal of dredged material for beneficial use offers potential for sustainable operations, but requires characterization with a high degree of confidence. Few data are available to inform characterization efforts in these artificial depositional environments; thus, a CDF case study was used to demonstrate a structured approach to sampling and data analysis. 相似文献167.
168.
Richard Michelmore Joan Wong 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(1):19-30
Lettuce downy mildew caused by Bremia lactucae has long been a model for understanding biotrophic oomycete–plant interactions. Initial research involved physiological and
cytological studies that have been reviewed earlier. This review provides an overview of the genetic and molecular analyses
that have occurred in the past 25 years as well as perspectives on future directions. The interaction between B. lactucae and lettuce (Lactuca sativa) is determined by an extensively characterized gene-for-gene relationship. Resistance genes have been cloned from L. sativa that encode proteins similar to resistance proteins isolated from other plant species. Avirulence genes have yet to be cloned
from B. lactucae, although candidate sequences have been identified on the basis of motifs present in secreted avirulence proteins characterized
from other oomycetes. Bremia lactucae has a minimum of 7 or 8 chromosome pairs ranging in size from 3 to at least 8 Mb and a set of linear polymorphic molecules
that range in size between 0.3 and 1.6 Mb and are inherited in a non-Mendelian manner. Several methods indicated the genome
size of B. lactucae to be ca. 50 Mb, although this is probably an underestimate, comprising approximately equal fractions of highly repeated
sequences, intermediate repeats, and low-copy sequences. The genome of B. lactucae still awaits sequencing. To date, several EST libraries have been sequenced to provide an incomplete view of the gene space.
Bremia lactucae has yet to be transformed, but regulatory sequences from it form components of transformation vectors used for other oomycetes.
Molecular technology has now advanced to the point where rapid progress is likely in determining the molecular basis of specificity,
mating type, and fungicide insensitivity. 相似文献
169.
Jesús Cerezo Valverde María D. Hernández Sandra García-Garrido Carmen Rodríguez Juán Estefanell Joan I. Gairín Carlos J. Rodríguez Ana Tomás Benjamín García García 《Aquaculture International》2012,20(1):71-89
In this study, HPTLC was used to make a quantitative analysis of the total lipid content (TL dry weight) and their classes
in 39 samples, including molluscs, crustaceans, fish and meals in an attempt to identify those most suitable for formulating
diets for cephalopods by reference to an index of nutritional quality (OILC: Oser’s index modified for lipid classes). All the crustaceans analysed (<10% TL), fish from artisanal fisheries such as
Boops boops, Gadus poutassou, Mugil sp. and Gadus minutus (<10% TL) and the plant meals (TL < 5%) would cause fewer digestive problems than the fish that were a by-catch from fish
farms (B. boops or Sparus aurata), pelagic species (Sardina pilchardus or Trachurus trachurus) or krill meal, which are characterised by their high lipid content (20–60% TL). These latter feeds were associated with
neutral lipids, mainly triglycerides during the summer. Mytilus galloprovincialis, Carcinus maenas, G. poutassou, Mugil sp., S. pilchardus and G. minutus had a more appropriate lipid content and profile during the winter, when they showed a higher OILC due to the greater variety of polar lipid classes they contained. Phospholipids like PS, PI and PE seem to be limiting nutrients
in cephalopods because of their high content (78–542, 41–309 and 152–2,114 mg/100 g, respectively) compared with the rest
of the samples. None of the meals analysed showed a good nutritional balance per se and should only be used in conjunction
with other foods. 相似文献
170.
Benjamin O. Knapp G. Geoff Wang Joan L. Walker 《Forest Ecology and Management》2008,255(11):3768-3777
Pine plantations in the southeastern United States are often created using site preparation treatments to alleviate site conditions that may limit survival or growth of planted seedlings. However, little is understood about how site preparations affect longleaf pine (Pinus palustris P. Miller) seedlings planted on wet sites. In a 2-year study (2004 and 2005) on poorly drained, sandy soils of Onslow County, North Carolina, we examined the effects of common site preparation treatments on microsite conditions and quantified relationships between microsite conditions and longleaf pine seedling survival and growth. Treatments used in the study included site preparations designed to control competing vegetation (chopping and herbicide) combined with those that alter soil conditions (mounding and bedding). During both years, mounding and bedding treatments reduced the amount of moisture within the top 6 cm of soil and increased soil temperatures when compared to flat planting (p < 0.001). Soil moisture was inversely related to seedling mortality in 2004 (r2 = 0.405) and inversely related to root collar diameter in 2005 (r2 = 0.334), while light was positively related to root collar diameter in 2005 (r2 = 0.262). Light availability at the seedling level was highest on treatments that effectively reduced surrounding vegetation. Herbicides were more effective than chopping at controlling vegetation in 2004 (p < 0.001) and 2005 (p = 0.036). Controlling competing vegetation, especially shrubs, was critical for increasing early longleaf pine seedling growth. 相似文献