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排序方式: 共有263条查询结果,搜索用时 0 毫秒
21.
A method for the detection of the effects of antibiotics on soil microbial communities was optimised in the present study. We investigated the influence of measurement time and nutrient status on the pollution-induced community tolerance (PICT), using the sulfonamide sulfachloropyridazine (SCP) as model compound. The tolerance development in soil microcosms that were exposed to SCP under different conditions was compared with the background tolerance in SCP-unexposed microcosms. The tolerance of bacterial extracts from the soil microcosms was determined in Biolog® multiwell plates as the SCP sensitivity of a range of physiological processes. The background tolerance was not affected by soil nutrient amendments, but an influence of the inoculum density in the microtiter plates was observed. Still, the variance of the background tolerance was low, which is in favour of the usage of community tolerance measurements for a selective detection of a toxicant impact. In line with the assumptions of the PICT concept, soil amendment with SCP led to an increase in community tolerance. This tolerance development was enhanced upon additional soil amendment with fresh pig slurry, and less by alfalfa meal addition. Tolerance increases were observed after a soil exposure to SCP of only 7 days, possibly because nutrient input facilitates the fast adaptation of the soil microbial community. However, a further increase in exposure time led to variable changes in the observed tolerance. Prolonged tolerance detection in the microtiter plates (11 days) enabled a clearer differentiation between different soil treatments, as it better resolved the EC50 values of processes with a high tolerance to bacteriostatic antimicrobial compounds. For the detection of antibiotic effects on soil microbial communities, it is therefore recommended to use nutrient amendments (possibly fresh pig slurry), to standardize the soil exposure time, and to extend the period of Biolog plate measurement beyond 7 days. 相似文献
22.
Augmentation of small rare species populations is sometimes suggested on genetic grounds. However, outbreeding depression via dilution of local adaptation or break-up of genomic coadaptation may occur. These effects depend on the causes of population divergence. Here, we compare genetic measures of population divergence in Liatris scariosa var. novae-angliae, a rare New England perennial. We measured GST, neutral marker subdivision, and QST, quantitative subdivision of propagule and juvenile plant traits. GST was relatively high. QST for leaf shape exceeded GST, indicating local adaptation, while QST for other traits fell within or below the GST range. Local adaptation appears low for juvenile traits, although the high GST cautions against translocation because of potential coadaptation. If translocation is still required, however, donor populations should contain high quantitative genetic diversity. We assess population size and allozyme diversity as predictors of quantitative genetic variation, but find these poor proxies for direct measurement. 相似文献
23.
Nitrate determination in leachates from farmyard manure by UV absorption A simple, sufficiently sensitive (< 1 ppm NO3?-N) method for nitrate determination in leachates from farmyard manure is described, suitable for routine analysis. The well known determination by UV absorption is preceded by a precipitation of organic matter with ZnSO4BO7. By this, average NO3?-N contents of 48.7 ppm were detected in leachates from cattle manure heaps (n = 54). 相似文献
24.
Nils Dittbrenner Hannah Schmitt Yvan Capowiez Rita Triebskorn 《Journal of Soils and Sediments》2011,11(6):1000-1010
Purpose
The use of only one or a few species—representing an entire taxon—in ecotoxicological standard tests poses risk of underestimating the impact of toxicants on the environment. In earthworm ecotoxicity tests, the species Eisenia fetida or Eisenia andrei are commonly used, and there is evidence that these species respond relatively insensitive towards environmental pollution. With the present study, we wanted to evaluate the risk of underestimating effects of the insecticide imidacloprid in soil organisms by comparing E. fetida with two other earthworm species (Aporrectodea caliginosa and Lumbricus terrestris) regarding their sensitivities towards soil contaminated with this widely used insecticide. 相似文献25.
I. V. Yevdokimov A. A. Larionova M. Schmitt V. O. Lopes de Gerenyu M. Bahn 《Eurasian Soil Science》2010,43(12):1373-1381
The contributions of root and microbial respiration to the total emission of CO2 from the surface of gray forest and soddy-podzolic soils were compared under laboratory and field conditions for the purpose
of optimizing the field version of the substrate-induced respiration method. The magnification coefficients of respiration
upon the addition of saccharose (k
mic) were first determined under conditions maximally similar to the natural conditions. For this purpose, soil cleared from
roots was put into nylon nets with a mesh size of 40 μm to prevent the penetration of roots into the nets. The nets with soil
were left in the field for 7–10 days for the compaction of soil and the stabilization of microbial activity under natural
conditions. Then, the values of k
mic were determined in the root-free soil under field conditions or in the laboratory at the same temperature and water content.
The contribution of root respiration as determined by the laboratory version of the substrate-induced respiration method (7–36%)
was lower compared to two field versions of the method (27–60%). Root respiration varied in the range of 24–60% of the total
CO2 emission from the soil surface in meadow ecosystems and in the range of 7–56% in forest ecosystems depending on the method
and soil type. 相似文献
26.
The formation of conjugates between beta-lactoglobulin and acacia gum based on electrostatic complexes formed at pH 4.2 was investigated upon dry-state incubation for up to 14 days at 60 degrees C and 79% relative humidity (RH). By means of SEC-HPLC and RP-HPLC, it was shown that the beta-lactoglobulin incubated alone was able to form polymers with molecular masses higher than 200 kDa until 50% of the initial monomeric protein disappeared after 14 days. In the presence of acacia gum at initial protein to polysaccharide weight mixing ratios of 2:1 and 1:2, only 35% of the initial beta-lactoglobulin monomers disappeared after 14 days. Using RP-HPLC, an apparent reaction order of 2 was found for the disappearance of monomeric beta-lactoglobulin both in the presence or absence of acacia gum. However, the reaction rate was faster in the absence of acacia gum. SDS-PAGE electrophoresis with silver staining confirmed the formation of beta-lactoglobulin/acacia gum conjugates. The solubility curves of the incubated beta-lactoglobulin showed a minimum around pH 4-5. By contrast, the minimum of solubility of the beta-lactoglobulin/acacia gum incubated mixtures shifted to lower pH values compared to initial mixtures. The conjugates exhibited higher foam capacity than the incubated protein as well as lower equilibrium air/water surface tension. Conjugation at ratio 1:2 led to increased interfacial viscosity (300 mN s m(-1) at 0.01 Hz) compared to beta-lactoglobulin alone (100 mN s m(-1) at 0.01 Hz), but similar interfacial elasticity (30-40 mN m(-1)). The foam capacity of the conjugates was significantly higher than that of the incubated beta-lactoglobulin as well as foam expansion and drainage time, especially at pH 5.3, i.e., higher than the pH of formation of the conjugates. 相似文献
27.
28.
André Fischer Sbrissia Daniel Schmitt Paulo Gonçalves Duchini Sila Carneiro Da Silva 《Journal of Agronomy and Crop Science》2020,206(5):630-639
It is well reported in the scientific literature that pastures can have similar net forage accumulation when managed with contrasting structures. However, we hypothesized that the dynamics of forage accumulation in grazed swards is linked to seasonal-environmental conditions. Marandu palisadegrass (Brachiaria brizantha [Hochst. ex A. Rich.] was used as the forage species model. The experimental treatments were four grazing heights (10, 20, 30 and 40 cm) allocated to experimental units according to a randomized complete block design with four replicates and evaluated throughout four contrasting environmental seasons (summer, autumn, winter–early spring and late spring). Under rainy and warm periods, greater net forage accumulation was observed in pastures maintained taller; on the contrary, during the mild and dry periods, net forage accumulation rate reduced as grazing height increased. Such patterns of responses were related to compensations between tiller population density and tissues flows during summer and late spring and the reduced capacity of taller canopies to compensate lower population with greater growth rates during autumn and winter–early spring. Grazed swards changed their patterns of forage growth as they transitioned from favourable to more abiotic stressful conditions, suggesting that seasonal adjustments in grazing intensities are necessary in order to maximize forage production. 相似文献
29.
Schmitt FO 《Science (New York, N.Y.)》1930,72(1875):583-584
30.