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1.
Constructed ponds are an important consideration in the conservation of wetland biota in agricultural landscapes. Twenty-two natural ponds and 22 adjacent constructed ponds (farm dams) were surveyed on the Southern Tablelands of New South Wales to compare patterns of use by frogs and develop frog conservation recommendations. Farm dams supported similar numbers of frog species to natural ponds, although differences in frog assemblage were observed between the pond types. Limnodynastes tasmaniensis and Uperolia laevigata were significantly more likely to occur at farm dams while L. peronii was more likely to occur at natural ponds. Results suggest waterbodies with high levels of emergent vegetation cover that lack fish are likely to support a high number of frog species, regardless of origin (i.e. natural or constructed). However, it is important for landholders to conserve natural waterbodies as these environments appear likely to support frog species that do not use farm dams. 相似文献
2.
Isolates of a soil Pseudoimonas, as well as other soil bacteria, showed a different sensitivity towards NO?2 when grown under aerobic or anaerobic conditions. The tolerance to NO?2 was increased in the presence of O2: for instance, a concentration of of NO?2-N proved to be toxic to a Pseudomonas sp. under anaerobic conditions, whereas over were needed aerobically to suppress its growth completely. The addition of NO?3 as an electron acceptor for anaerobic respiration did not overcome the inhibitive effect of NO?3. The pH range, at which NO?2 was utilized anaerobically, was narrowed with increasing NO?2 concentration (pH 6.8–8.8 at of NO?2-N and 7.4–8.5 and of NO?2-N).Tolerance to nitrite varied considerably among the bacteria tested. Each species was able to overcome the inhibitory effect of NO?2 up to a certain concentration, while the length of the lag phase was related to NO?2 concentration. 相似文献
3.
Leroy EM Rouquet P Formenty P Souquière S Kilbourne A Froment JM Bermejo M Smit S Karesh W Swanepoel R Zaki SR Rollin PE 《Science (New York, N.Y.)》2004,303(5656):387-390
Several human and animal Ebola outbreaks have occurred over the past 4 years in Gabon and the Republic of Congo. The human outbreaks consisted of multiple simultaneous epidemics caused by different viral strains, and each epidemic resulted from the handling of a distinct gorilla, chimpanzee, or duiker carcass. These animal populations declined markedly during human Ebola outbreaks, apparently as a result of Ebola infection. Recovered carcasses were infected by a variety of Ebola strains, suggesting that Ebola outbreaks in great apes result from multiple virus introductions from the natural host. Surveillance of animal mortality may help to predict and prevent human Ebola outbreaks. 相似文献
4.
Fournand D Vicens A Sidhoum L Souquet JM Moutounet M Cheynier V 《Journal of agricultural and food chemistry》2006,54(19):7331-7338
Quantitative and qualitative modifications of tannins and anthocyanins in grape skin were investigated at different dates of harvest, from berries sorted on the basis of their density. Free anthocyanins accumulated until 170 g/L of sugars in pulp before undergoing a slight decrease. Changes in anthocyanin composition were observed with increasing sugar levels in the pulp that reflected structural differences between classes of anthocyanins. The proportion of methoxylated anthocyanins continued to increase in the skin as sugar accumulated while the proportion of coumaroylated anthocyanins initially increased (up to 200 g/L of sugars in the pulp) and then rapidly decreased. In comparison, no major quantitative nor qualitative change was observed for tannins, except for a slight increase of the mean degree of polymerization. Whatever the physiological stage of the pulp, the extraction yield of skin phenolics into hydroalcoholic solution for 5 h was lower than 77% for anthocyanins and 38% for proanthocyanidins. For both classes of compounds, no clear evolution in these extraction yields could be observed as sugars accumulated in pulp (from 162.6 to 275.0 g/L). Nevertheless, some structural features within each family of compounds significantly influenced extractability, for example, a lower extraction yield for coumaroylated anthocyanins and for tannins with a high degree of polymerization. Finally, no direct relationship could be found in extraction media between the amounts of all red pigments (measured in acidic conditions) and the color intensity at 520 nm (measured in wine-like model solutions). 相似文献
5.
Jean-Marc Ducruet Hortensia Sixto Jos-María Garcia-Baudin 《Pest management science》1993,38(4):295-301
Chlorophyll fluorescence induction was used as a probe to detect herbicide detoxification in tolerant or susceptible wheat cultivars. Experimental conditions have been carefully examined for establishing detoxification kinetics of chlorotoluron and metribuzin, two photosystem-II-inhibiting herbicides. After a root treatment, leaves were cut, placed in glass tubes and maintained in the dark. The fluorescence induction rise was examined repeatedly and detoxification kinetics were established from these data for the same position on the individual leaves. The herbicide-dependent fluorescence rise decreased within hours in chlorotoluron-tolerant but not in susceptible Triticum aestivum cultivars. In contrast, no significant reversion could be detected after metribuzin application in both tolerant and susceptible cultivars of Triticum durum. Near the fluorescence-determined half-inhibition of photosystem II, linear detoxification kinetics were obtained in individual leaves, thus providing an accurate measurement of relative detoxification rates. 相似文献
6.
7.
We tested whether synchronous, long‐term fluctuations in Atlantic bluefin tuna (Thunnus thynnus) trap catches, collected from the ancestral Mediterranean and Atlantic trap fishery, might be related to large‐scale environmental change. Nine time series of trap catches of more than 80 yr long were compared with long time series of three preselected environmental variables, i.e. the North Atlantic Oscillation (NAO), the Length of the Day Index (LOD, a proxy of the atmospheric circulation index) and the temperature. Spectral analyses of trap catches, LOD and temperature displayed similar spectra with peaks at low frequencies, whereas those of the NAO exhibited a broad band spectrum. Regression analyses and tests of correlation did not reveal any clear relationship between trap catches on the one hand and NAO and LOD on the other hand. In contrast, long‐term fluctuations in trap catches appear to be closely and negatively related to long‐term trends in temperature. Underlying processes that could explain such a relationship are discussed, with special focus on changes in migration patterns of the Atlantic bluefin tuna. 相似文献
8.
Major sugar and carboxylic acid components in apricot flesh fruits were detected and quantified. Fifty-one genotypes including
clones growing in France, Spain, Italy, Greece and USA, belonging to the INRA germ plasm collection has been evaluated. Principal
component analysis (PCA) has been performed to study correlation among fruit quality measurements and to interpret relationships
between genotypes as a tool for germ plasm characterization. A marked variation in malic and citric acid content has been
observed and PCA revealed clusters of apricot genotypes for the malic/citric ratio content. A good correlation between sugar
component and refractometer index (r = 0.83) has been detected. The wide range of diversity in malic and citric acid content in apricot germ plasm makes it possible
to breed and select genotypes with improved flavour on the basis of superior phenotypes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
9.
Diurnal raptors were surveyed in Central Sulawesi on foot in 16 sample areas, and by car along 2700 km road transects in August-September 2000. All 23 resident species were recorded and their frequency of occurrence assessed in broad habitat categories. Farmlands were unusually poor in raptors. Of their six associated species, the formerly common black kite (Milvus migrans) may be almost extirpated. Indiscriminate pesticide use is suspected to be a major factor. Wetlands and sea-coasts are limited in area and are also the most heavily disturbed natural habitats. All four piscivorous eagles were found to be rare or very local. Among them, only the grey-headed fishing-eagle (Ichthyophaga ichthyaetus) was found to be more frequent than was previously known. Excessive human fishing pressure may be the main threat, together with extensive wetland conversion into ricefields or fishponds. Forest raptors (13 species), including all Sulawesi endemic Falconiformes, were the most numerous and widespread birds of prey. Although they exhibited a fairly high tolerance to forest degradation and fragmentation (insular syndrome), their main threat is the high deforestation rate, especially the loss of the presumably more productive lowland forests. 相似文献
10.
Dimeric and polymeric hybrid oliogmers were obtained by the reaction of 2,6-xylenol and syringic acid in the presence of an enzyme from the fungus Trametes versicolor. Three hybrid dimers were formed in an assay at pH 4.5, while at pH 6.5, the formation of additional higher polymers with a phenyl-ether bond (tail to head linkage) was detected. The major product was identified as 3,5-dimethyl-3′,5′-dimethoxydiphenoquinone (4,4′), and it amounted to approximately 45% of the applied 2,6-xylenol after 3.5 hr incubation at pH 4.5. About 8% of the 2,6-xylenol was transformed to 4,4′-dihydroxy-3,5-dimethyl-3′,5′-dimethoxydiphenol and 22% to 3-methoxy-5-(2′,6′-dimethylphenoxy)-benzoquinone (1,2). 相似文献