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101.
DM Magalhães DD Fernandes MBS Mororó CMG Silva GQ Rodrigues JB Bruno MHT Matos CC Campello JR Figueiredo 《Reproduction in domestic animals》2011,46(1):134-140
The aim of the present study was to evaluate the effects of different medium replacement intervals on the viability, antral cavity formation, growth and in vitro maturation (IVM) of oocytes from caprine and ovine pre‐antral follicles. Pre‐antral ovarian follicles (≥150 μm) were isolated from the ovarian cortex of goats and sheep and were individually cultured for 24 days using two different medium replacement intervals [2 days (T1) or 6 days (T2)]. Follicle development was evaluated on the basis of antral cavity formation, increases in follicular diameter and the presence of healthy cumulus oocyte complexes and fully grown oocytes. For caprine species, results showed a higher percentage (p < 0.05) of viable follicles in T1 than T2 from day 6 until the end of the culture. In addition, when comparing both treatments after the same culture duration, the rate of antrum formation was significantly higher in T1 than in T2 from day 12 onwards. Yet, in ovines, when both treatments were compared on day 24 of the culture, there were more viable follicles in T2 than in T1 (p < 0.05). In the caprine species, percentages of fully grown oocytes (≥110 μm) acceptable for IVM after 24 days of culture were significantly higher in normal follicles cultured in T1 (30.0%) than in T2 (6.7%; p < 0.05). On the other hand, in ovines, at the end of the culture, the percentage of oocytes destined for IVM was higher in T2 than in T1 (23.5% vs 2.9%; p < 0.05). In conclusion, under the same conditions, the frequency of medium replacement significantly affected the in vitro development of caprine and ovine pre‐antral follicles. To improve the efficiency of the culture system, the medium must be replaced every 2 and 6 days for goat and sheep pre‐antral follicles, respectively. 相似文献
102.
103.
104.
Scott C. Chapman 《Euphytica》2008,161(1-2):195-208
Crop simulation models of plant processes capture the biological interactions between the sensing of signals at an organ level
(e.g. drought affecting roots), the response of the plant at a biochemical level (e.g. change in development rate) and the
result at the organ (or crop) level (e.g. reduced growth). In dissecting the complex control of phenotypes like yield, simulation
models have several roles. Models have been used to generate an index of the climatic environment (e.g. of drought stress)
for breeding programme trials. In wheat and sorghum grown in northern Australia, this has shown that mid-season drought generates
large genotype by environment interaction. By defining gene action to calculate the value of input trait parameters to crop
models, simulated multi-environment trials estimate the yield of ‘synthetic’ sorghum cultivars grown in historical or artificial
climates with current or potential management regimes. In this way, the biological interactions among traits constrain the
crop yields to only those that are biologically possible in the given set of environments. This allows the construction of
datasets that are more ‘realistic’ representations of gene by trait by environment interaction than is possible using only
the statistical attributes (e.g. means, variances and correlations) of real-world trait datasets. This approach has an additional
advantage in that ‘biological and experimental noise’ can be manipulated separately. These ‘testbeds’ for statistical techniques
can be extended to the interpretation of a crossing and selection programme where the processes of chromosomal recombination
are simulated using a quantitative genetics model and applied to the trait parameters. Statisticians are challenged to develop
improved methods for the resulting simulated phenotype datasets, with the objective of revealing the (known) underlying genetic
and environment structure that was input to the simulations. These improved methods can then be applied to existing plant
breeding programmes. 相似文献
105.
The dairy industry in southern Australia relies on perennial ryegrass pasture to supply 60–70% of the diet of lactating cows. Improvements in the amount and quality of home-grown forage used for dairy cow feeding are critical for further productivity gains in the industry. A modeling approach was used to estimate the effects of changing the forage system on farm business profit. Base models (using 100% of farm area in perennial ryegrass pasture) were constructed for above-average (Top 40%) and high performing (Top 10%) farm types typical of two locations: Terang in southwest Victoria and Ellinbank in Gippsland, eastern Victoria. These models were then re-simulated using different forage base options such as: oversowing annual ryegrass, winter crops (annual ryegrass monoculture, winter cereal grown for whole crop silage), summer crops (grazing brassicas, maize), combinations of these (double cropping), or summer shoulder pasture (notionally based on tall fescue) on between 10% and 100% of farm area. 相似文献
106.
E. Emily V. Chapman G?ran Dave John D. Murimboh 《Water, air, and soil pollution》2012,223(6):2907-2922
To accurately assess the risks of metal contaminants in soil, the bioavailability of the metals need to be considered. The bioavailable concentrations determined from homogenized, dried soils are not necessarily representative of in situ conditions of undisturbed field soils. In this study, we investigated the accumulation of metals in wheat (Triticum aestivum) grown in undisturbed contaminated (Pb, Zn, Cu, and Cd) soil cores, in relation to total soil, leachate, and diffusive gradients in thin films (DGT)-labile metal concentrations. Despite the fact that many of the samples contained metal concentrations above guideline values, no significant effects were observed on wheat growth. The bioavailability of metals in the most contaminated samples was estimated to be medium to low, possibly explaining why few effects were observed in the bioassay. For Cu, Zn, and especially for Pb, leachate and DGT-labile concentrations were better predictors of uptake by wheat than total concentrations based on correlations. It is suggested that DGT and leachate concentrations in combination with bioassays in undisturbed soil cores can be used to account for metal bioavailability in soil. These tests could be used during the ecological risk screening stage, in conjunction with total concentrations and guideline values to better estimate receptor exposure. 相似文献
107.
Yaying Li Juan Wang Fuxiao Pan Stephen James Chapman Huaiying Yao 《Journal of Soils and Sediments》2016,16(5):1472-1480
Purpose
Soil microorganisms are important in the cycling of plant nutrients. Soil microbial biomass, community structure, and activity are mainly affected by carbon substrate and nutrient availability. The objective was to test if both the overall soil microbial community structure and the community-utilizing plant-derived carbon entering the soil as rhizodeposition were affected by soil carbon (C) and nitrogen (N) availability.Materials and methods
A 13C-CO2 steady-state labeling experiment was conducted in a ryegrass system. Four soil treatments were established: control, amendment with carboxymethyl cellulose (CMC), amendment with ammonium nitrate (NF), combined CMC and NF. Soil phospholipid fatty acid (PLFA) and 13C labeling PLFA were extracted and detected by isotope ratio mass spectrometer.Results and discussion
The combined CMC and NF treatment with appropriate C/N ratio (20) significantly enhanced soil microbial biomass C and N, but resulted in lower soil inorganic N concentrations. There was no significant difference in soil PLFA profile pattern between different treatments. In contrast, most of the 13C was distributed into PLFAs 18:2ω6,9c, 18:1ω7c, and 18:1ω9c, indicative of fungi and gram-negative bacteria. The inorganic-only treatment was distinct in 13C PLFA pattern from the other treatments in the first period of labeling. Factor loadings of individual PLFAs confirmed that gram-positive bacteria had relatively greater plant-derived C contents in the inorganic-only treatment, but fungi were more enriched in the other treatments.Conclusions
Amendments with CMC can improve N transformation processes, and the ryegrass rhizodeposition carbon flux into the soil microbial community is strongly modified by soil N availability.108.
This paper describes a field study to assess the effect of increasing the frequency of split applications of N fertiliser on the pattern of plant uptake, soil N availability, and microbial biomass C and N. Measurements were taken during the growing season in different positions relative to young trees (Prunus avium L.) in an upland silvopastoral system in its first year after establishment. At fertiliser rates of 72 and 144 kg ha-1 N applied as NH4NO3, increasing the number of split applications increased N uptake by the pasture. Mineral forms of soil N measured 2 weeks after application indicated that residual NH
inf4
sup+
-N and total mineral N were also greater in this treatment on certain dates. Soil NO
inf3
sup-
-N was positively correlated with the soil moisture content, and nitrification reached a maximum in early May and declined rapidly thereafter except within the herbicide-treated areas around the trees where soil moisture had been conserved. Results of the study suggest that high NO
inf3
sup-
-N in herbicide-treated areas was probably caused by mineralisation of grass residues and low uptake by the tree rather than by preferential urine excretion by sheep sheltering beside the trees. Mean microbial biomass C and N values of 894 and 213 kg ha-1, respectively, were obtained. Microbial C was slightly increased by the higher frequency of split applications at 144 kg ha-1 N and was probably related to the greater herbage production with this treatment. Microbial N was not significantly affected by the N treatments. Both microbial biomass C and N increased during the growing season, resulting in the net immobilisation of at least 45 kg ha-1 N which was later released during the autumn. 相似文献
109.
Distribution of phosphorus in soil aggregate fractions and its significance with regard to phosphorus transport in agricultural runoff 总被引:1,自引:0,他引:1
Z. L. He M. J. Wilson C. O. Campbell A. C. Edwards S. J. Chapman 《Water, air, and soil pollution》1995,83(1-2):69-84
Surface runoff is the major way of P transport from agricultural land to surface waters. To assess the potential of P loss in runoff in relation to soil P status, the chemical nature and distribution of soil P in different size classes of water-stable aggregates were quantified for two distinctive soil types. For both soils unfertilized areas under pasture and well-fertilized arable soils were sampled. The content of total P, organic P and microbial biomass P (Pmic) decreased in the aggregate size order <0.1, 1–2, and 0.1–1.0 mm respectively. In contrast available P (extracted by Bray I reagent) was lowest in the <0.1 mm aggregate size. Cultivation decreased the percentage of 1–2 mm aggregates but increased that of the <0.1 mm aggregates. Fertilization increased markedly both total P and organic P in the <0.1 mm fraction of arable soils compared to the corresponding samples from unfertilized grassland soils. During aggregate separation, most of P loss was in the form of particulate P and less than 1% in solution. More organic P and Pmic were lost from the grassland soils than from the arable soils. 相似文献
110.
Differences in nitrogen‐assimilating enzyme activity in halophyte species are habitat‐related 下载免费PDF全文
The chemical form and content of available nitrogen (N) in salt marsh substrates varies considerably. On the western coast of Ireland, habitats designated as Ombrogenic Atlantic salt marshes were formed on ombrogenic peat substrate. The peat substrate in these systems has three times more ammonium than substrate from adjacent salt marsh habitats on sand and mud substrate. This study examined the extent to which the high concentration of ammonium in peat salt marsh substrate influences the N‐ assimilating enzyme activity of halophytes and the extent to which N metabolism differs between species. Specifically, this work investigated whether plants from peat salt marshes are more likely to assimilate ammonium than plants from non‐peat substrates. Four halophyte plant species—Armeria maritima, Aster tripolium, Plantago maritime, and Triglochin maritime—were sampled from various saltmarsh habitats including three sites on peat substrate and three on non‐peat substrate, comprising sand, mud and sand/mud. The activities of N‐metabolising enzymes—glutamine synthetase (GS), glutamate synthase, glutamate dehydrogenase (GDH), and nitrate reductase (NR)—were quantified in shoot and root parts. Root GS activity in Armeria maritima and shoot GS activity in Triglochin maritima were positively correlated with increasing soil ammonium levels. Root NR activity in Aster tripolium and shoot NR activity in Plantago maritima were significantly higher in plants grown on non‐peat substrates than peat substrates. The shoot : root GS activity ratio in Triglochin maritima on peat substrate was more than double the ratio on non‐peat substrates. It is concluded that all species tested displayed differences in N‐metabolising activities depending on the chemical form and/or concentration of N in the substrate, while three out of the four species were capable of taking advantage of the high levels of ammonium in peat substrates. 相似文献