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1.

Background  

Heavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulp- and paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies.  相似文献   

2.
In the coastal countries of East Asia and Southeast Asia, ciguatera should be common because of the extensive tropical and subtropical coral reefs along the coasts and in the neighboring seas with ciguatoxic fishes. An extensive search of journal databases, the Internet and the government websites was performed to identify all reports of ciguatera from the regions. Based on the official data and large published case series, the incidence of ciguatera was higher in the coastal cities (Hong Kong, Foshan, Zhongshan) of southern China than in Japan (Okinawa Prefecture). In Singapore, ciguatera appeared to be almost unknown. In other countries, only isolated cases or small case series were reported, but under-reporting was assumed to be common. Ciguatera may cause severe acute illness and prolonged neurological symptoms. Ciguatera represents an important public health issue for endemic regions, with significant socio-economic impact. Coordinated strategies to improve risk assessment, risk management and risk communication are required. The systematic collection of accurate data on the incidence and epidemiology of ciguatera should enable better assessment and management of its risk. Much more work needs to be done to define the size threshold for important coral reef fish species from different regions, above which the risk of ciguatera significantly increases.  相似文献   

3.
The causes of high biological diversity in biodiversity hotspots have long been a major subject of study in conservation biology. To investigate this matter, we conducted a phylogeographic study of five Drosophila (Diptera: Drosophilidae) species from East and Southeast Asia: Drosophila albomicans Duda, D. formosana Duda, D. immigrans Sturtevant, D. melanogaster Meigen, and D. simulans Sturtevant. We collected 185 samples from 28 localities in eight countries. From each collected individual, we sequenced the autosomal extra sex comb gene (esc) and seven mitochondrial genes, including nicotinamide adenine dinucleotide hydrate-reductase dehydrogenase subunit 4 (ND4), ND4L, tRNA-His, tRNA-Pro, tRNA-Thr, partial ND5, and partial ND6. Phylogenetic analyses using maximum- likelihood and Bayesian methods revealed interesting population structure and identified the existence of two distinct D. formosana lineages (Southeast Asian and Taiwanese populations). Genetic differentiation among groups of D. immigrans suggests the possibility of endemic speciation in Taiwan. In contrast, D. melanogaster remained one extensively large population throughout East and Southeast Asia, including nearby islets. A molecular clock was used to estimate divergence times, which were compared with past geographical events to infer evolutionary scenarios. Our findings suggest that interglacial periods may have caused population isolation, thus enhancing population differentiation more strongly for some of the Drosophila species. The population structure of each Drosophila species in East and Southeast Asia has been influenced by past geographic events.  相似文献   

4.
Population genetic studies may provide crucial information for our knowledge on human peopling history and have been extensively applied to reconstruct East Asian prehistory in the last 10 years. However, different genetic investigations are not always consistent with each other and some results are conflicting or misinterpreted. This represents a main obstacle for scholars of other disciplines like archaeologists and linguists who try to relate the genetic information on past human migrations to their own results on the spread of domesticated crops or animals or on the dispersal of the main language families. In this paper, we review the current genetic evidence related to the peopling history of East Asia with a critical view on some interpretations. In this way, we hope to provide a useful reference for further interdisciplinary studies on our past.  相似文献   

5.
Good quality gluten-free products continue to be in demand among the celiac community and the production of pasta from non-conventional raw materials is a major technological challenge. In this work, the effects of two different pasta-making processes (conventional and extrusion-cooking) were investigated on parboiled brown and milled rice flours. The two processes differentiated for extrusion temperature (conventional extrusion: 50 °C, max; extrusion-cooking: 115 °C), whereas the drying diagram was the same. Starch modifications induced by each pasta-making process were analyzed by using a Micro-ViscoAmylo-graph (MVAG), Differential Scanning Calorimetry (DSC), and X-ray Diffraction. The cooking quality was evaluated by weight increase, solid loss into the cooking water, and texture analysis. Pasta obtained from milled rice using the extrusion-cooking process was characterized by the best cooking behavior. In this sample, starch presented the highest peak and final viscosities, the highest gelatinization temperature and lower enthalpy value, and the lowest crystallinity. The cooking quality of pasta obtained from brown rice appeared less affected by the processing conditions. Therefore, the nature and intensity of starch modifications can be modulated by the processing conditions and might explain the different cooking behaviour of rice pasta.  相似文献   

6.

Background

In the androdioecious nematode Caenorhabditis elegans virtually all progeny produced by hermaphrodite self-fertilization is hermaphrodite while 50% of the progeny that results from cross-fertilization by a male is male. In the standard laboratory wild type strain N2 males disappear rapidly from populations. This is not the case in some other wild type isolates of C. elegans, among them the Hawaiian strain CB4856.

Results

We determined the kinetics of the loss of males over time for multiple population sizes and wild isolates and found significant differences. We performed systematic inter- and intra-strain crosses with N2 and CB4856 and show that the males and the hermaphrodites contribute to the difference in male maintenance between these two strains. In particular, CB4856 males obtained a higher number of successful copulations than N2 males and sired correspondingly more cross-progeny. On the other hand, N2 hermaphrodites produced a higher number of self-progeny, both when singly mated and when not mated.

Conclusion

These two differences have the potential to explain the observed variation in male persistence, since they should lead to a predominance of self-progeny (and thus hermaphrodites) in N2 and, at the same time, a high proportion of cross-progeny (and thus the presence of males as well as hermaphrodites) in CB4856.  相似文献   

7.
Three grass silages made in sunny weather in early July from second-harvest perennial ryegrass were compared in a 16-week feeding experiment with twelve Ayrshire cows. The silages were either unwilted or wilted with and without conditioning, and had mean dry matter (DM) concentrations of 201, 261 and 272 g kg−1, and in vitro DOMD concentrations of 650, 669 and 672 g kg−1 DM respectively. All the silages had formic acid ('Add-F') applied at a rate of 2.6 litres t−1 and were offered ad libitum plus 6 kg concentrates per cow per d. The daily intakes of silage DM were 905 kg per cow on the unwilted treatment and 9.86 and 9.65 kg on the wilted treatments with and without conditioning respectively. Daily milk yields were 171, 17.6 and 17.4 kg per cow on the unwilted, and wilted with and without conditioning treatments respectively and were not significantly different. Fat concentrations in the milk were not affected significantly by treatment, whereas the crude protein and solids-not-fat concentrations were significantly higher on the wilted than on the unwilted treatment. The efficiency of utilization of metabolizable energy for lactation was 6–7% lower with the wilted than with the unwilted silages and it is concluded that the unwilted silage was superior to the wilted silages as a feed for dairy cows.  相似文献   

8.
Three grass silages made in early June from S23 perennial ryegrass were compared in a 16-week feeding experiment with twelve Ayrshire cows. The silages were made from uniform herbage which received either formic acid (‘Add-F’) at the rate of 201 t?1, or a formalin-sulphuric acid mixture (‘Syiade’) at rates of 2.0 and 4.4 1 t?1. The silages were offered ad libitum either alone or supplemented with a cube containing 38% CP in the DM at the rate of 1.4 kg per 10 kg milk. The daily intakes of silage DM were not significantly different on the three silage treatments, and averaged 10.7, 11.0 and 11.0 kg per cow on the formic acid and the 2.0 and 44 1 t?1 formalin-acid treatments respectively. The mean daily yields of milk were 15.1, 13.3 and 13.7 kg per cow in the unsupplemented treatments, and 18.2, 18.1 and 18.0 kg per cow in the supplemented treatments on the formic acid and the 2.0 and 44 1 t?1 formalin-acid treatments respectively. On the basis of total animal production expressed in terms of metabolizable energy requirements, it was concluded that the differences between the three silages were small.  相似文献   

9.
Three first-harvest grass silages made from S23 perennial ryegrass cut on 25 May, 13 June and 25 June, and termed early, medium and late silages respectively, were compared in a 16-week feeding experiment with fourteen Ayrshire cows. The early, medium and late silages had D-values of 71·2, 65·0 and 62·5 respectively. The early silage was offered alone, whereas the medium and late silages were supplemented with a concentrate containing 208 g crude protein per kg DM at rates of 2, 3 and 4 kg per 10 kg milk. Silage DM intake was 12·8 kg per cow per d on the early silage treatment, and decreased progressively as concentrate intake increased on the other silage treatments. The mean daily milk yields were 16·0 kg per cow in the early silage treatment, 17·0, 18·4 and 20·4 kg per cow in the medium silage treatments, and 16·8, 18·1 and 20·2 kg per cow in the late silage treatments on the 2-, 3- and 4-kg concentrate treatments respectively. Fat concentration in the milk was not affected significantly by treatment, whereas the CP and SNF concentrations increased progressively and significantly as supplementary feeding increased. From the relationship between milk yield and concentrate intake it was calculated that the medium and late silages required a daily concentrate supplement of 2·1 kg DM per cow to give the same daily milk yields as the early silage.  相似文献   

10.
Four grass silages of two chop lengths and two D-values were made from S23 perennial ryegrass, and compared in a feeding experiment with lactating cows and in an eating-behaviour study with non-lactating cows. The median chop lengths were 11·6 and 11·5 mm in the short silages and 18·2 and 19·5 mm in the medium silages. Chop length had negligible effects on D-value and on pH with values of 3·81 and 3·94 on the short and medium silages respectively.
Silage DM intakes were higher on the short than on the medium-chop silages in both experiments except where the high D-value silage was supplemented with concentrates. Milk yields were not affected significantly by chop length with daily values of 19·3 and 19·7 kg per cow on the short and medium treatments respectively with the high D-value silage, and 18·2 and 18·3 kg per cow with the low D-value silage. Chop length had only small and non-significant effects on milk composition.
Eating times expressed as min per kg DM were significantly lower on the short than on the medium-chop silages.
It is concluded that the small differences between the short- and the medium-chop silages were of no economic importance.  相似文献   

11.
西双版纳热带雨林树种多度与丰富度空间分布特征   总被引:1,自引:0,他引:1  
兰国玉  朱华  曹敏 《热带作物学报》2011,32(6):1086-1092
基于西双版纳20 hm2森林动态监测样地内直径≥1cm的树种资料,分析该样地树种多度(个体数)和丰富度(物种数)及其方差与变异系数在7个取样尺度(5 m×5 m,10 m×10 m,20 m×20 m,25 m×25 m,50 m×50 m,100 m×100 m,200 m×250 m)的变化规律。结果显示:(1)西双版纳热带雨林样地环境异质性较大,多度和丰富度随着尺度的增加均表现非线性增加。(2)多度的方差随尺度增加而线性增加;丰富度的方差与尺度都表现出非线性的关系。丰富度的方差在尺度100 m×100 m上最大。(3)多度、丰富度和多样性指数的方差、变异系数均大于随机分布模型拟合的数值,表明树种在样地内分布不是随机分布。总之,在生物多样性的保护和管理中要特别注意,尽管多度具有可加性,只有当环境异质性不大时用小尺度多度估计大尺度多度才比较可靠;丰富度的非线性变化使得一个尺度上生物多样性"热点",在另一个取样尺度上却可能为"冷点"。  相似文献   

12.
Two grass silages made from perennial ryegrass, and with D-values of 0·216 and 0·255, were offered ad libitum to 18 Ayrshire cows in two feeding experiments. On the control treatment the silages were supplemented with soybean meal only, and on the other two treatments with equal weights of DM from either barley or dried molassed sugar-beet pulp plus the same weight of soya as on the control treatment. The daily intakes of silage DM were not significantly different on the barley and beet-pulp treatments, and, on average, the intake of silage DM was reduced by 0·24 and 0·20 kg by feeding 1 kg barley and beet pulp DM respectively.
The daily milk yields were not significantly different on the barley and beet-pulp treatments with mean values of 19·2 and 19·2 kg per cow respectively compared with 17·2 kg on the control treatment. On the barley and beet-pulp treatments the fat, SNF, CP and lactose concentrations in the milk and the live weights of the cows were not significantly different. It is concluded that the barley and beet pulp had similar feeding values and replacement rates when used as supplements with grass silage, and that the two feeds were interchangeable on an equal DM basis.  相似文献   

13.
Grass silage made in May from S24 perennial ryegrass was offered ad libitum to twelve Ayrshire cows in a 12-week feeding experiment. The silage had a DM concentration of 217 g kg -1, contained 147 g crude protein per kg DM and had a D-value of 64·6. In addition each cow consumed 1 kg hay per d plus concentrate supplements of dried sugar-beet pulp with (A) soya bean meal, (B)‘Pruteen’, a single-cell protein (C) groundnut cake. The three concentrate supplements each contained 250 g crude protein per kg DM and were offered at the rate of 2·9 kg per 10 kg milk. The daily intakes of silage DM were 8·38, 7·94 and 7·49 kg on treatments A, B and C, respectively, with the extreme values being significantly different. The mean daily yields of milk on treatments A and B were both 16·2 kg per cow, and were significantly higher than the yield of 15·2 kg per cow on treatment C. The fat and lactose contents of the milk on the three treatments were not significantly different, but the CP content on treatment C was significantly lower than that on the other treatments. It is concluded that soya bean meal and‘Pruteen’were superior to groundnut cake as a protein supplement in a silage-based ration.  相似文献   

14.
Silage made from Blanca white clover was offered ad libitum to four Friesian cows in a 12-week changeover experiment. The silage contained 990 g white clover DM (kg DM)−1 with 254 g DM kg−1 and 243 g CP (kg DM)−1 The pH was 3.98 and the in vitro DOMD concentration 680 g kg−1. The silage was the sole feed in the control treatment; in the other three treatments it was supplemented with barley, soybean meal, and a mixture of these feeds supplying 8.1, 2.7 and 7.8 kg DM per cow respectively. The daily intakes of silage DM were 19.3, 13.5, 17.5 and 13.5 kg per cow, and the daily milk yields were 26.3, 28.0, 28.6 and 27.6 kg per cow on the control, barley, soybean and barley plus soybean treatments respectively. It is concluded that the white clover silage had an excellent fermentation and a large potential for milk production.  相似文献   

15.
段红星  杨娜 《茶叶》2011,37(3):150-152
本文随机选取了产自云南的三个普洱熟茶茶样和产自广西的三个六堡茶茶样,分别对其主要内含成分(茶多酚、氨基酸、茶多糖、水浸出物、咖啡碱)含量进行测定,其后,对六个茶样进行感官审评,旨在分析比较普洱熟茶和六堡茶的品质特点及差异。通过实验,结果表明:普洱熟茶和六堡茶都各具地方特色,品质差异明显。  相似文献   

16.
Grass silage made in late May from S24 perennial ryegrass was offered to twelve Ayrshire cows in a 16-week feeding experiment. The silage had a DM content of 25.3%, a pH of 3.91, and contained 16.8% CP and 68.4% digestible organic matter in the DM. The silage was fed ad libitum and was the sole feed in the control treatment. In the other three treatments the silage was supplemented with a cube offered at rates of 0.8, 1.4 and 2.0 kg per 10 kg milk. The cube contained 82.2% groundnut, plus molasses and minerals, and had 37.9% CP in the DM. The daily intake of silage DM was 11.4 kg per cow on average over the four treatments which did not differ significantly. The mean daily milk yields were 14.8 kg per cow in the control treatment, and 16.5, 18.2 and 18.4 kg in the 0.8, 1.4 and 2.0 kg supplement treatments respectively. The SNF, CP and lactose contents of the milk were Wghest on the 1.4 kg supplement treatment. It is concluded that with a high digestibility silage, there is little evidence to support the feeding of more than 1.4 kg of high-protein cubes per 10 kg milk in the declining phase of lactation.  相似文献   

17.
Dactylis glomerata and Holcus lanatus were grown together in boxes with either full competition, root competition only, shoot competition only or no competition between them. The boxes were either fertilized (150 kg ha-1N, 100 kg ha-1 K, 80 kg ha-1 P) or not fertilized. The experiment was continued for 13 months, and a total of six cuts were taken.
H. lanatus was more competitive than D. glomerata throughout the experiment, though the effect declined after flowering during the second growing season. The effects of root competition were generally much greater than those of shoot competition and tended to increase during the first year. However, the effects of root competition declined, relative to shoot competition, after flowering in the second growing season.
Fertilizer applications slightly increased the root competitive ability of H. lanatus relative to D. glomerata but slightly reduced its shoot competitive ability.  相似文献   

18.
Grass silages made from first-harvest perennial ryegrass in mid-May and early-June and termed high-D and low-D respectively had mean DOMD values of 694 and 633 g kg−1 and were offered ad libitum to twelve Ayrshire cows in a 16-week feeding experiment using a cyclic changeover design. The silages were supplemented with a concentrate containing 363g CP per kg DM at daily rates of 1.5, 3.0 and 4.5 kg per cow. The average daily intakes of silage DM were 12.6 and 11.1 kg per cow on the high- and low-D silage treatments respectively, and were not significantly different on the three concentrate treatments. The mean daily milk yields were 171, 18.6 and 21.0 kg per cow on the low-D silage treatments, and 19.6, 21.2 and 22.8 kg per cow on the high-D silage treatments at the 1.5, 3.0 and 4.5 kg rates of concentrate feeding respectively. Fat and lactose concentrations in the milk were not affected significantly by treatment, whereas the CP and SNF concentrations increased progressively and significantly as the rate of supplementary feeding increased. It is concluded that a high-protein concentrate supplement allows silage to make the maximum contribution in the diet, and gives a high response in terms of milk yield and composition.  相似文献   

19.
Grass silage made in May from S24 perennial ryegrass had a DM concentration of 262 g kg-1 and an in vitro D-value of 0·698, and was given ad libitum to twelve Ayrshire cows in a 16-week feeding experiment. In addition supplements of hay with a mean in vitro D-value of 0·603 were offered in one of three forms—long, chopped (12·1 mm) or ground (0·80 modulus of fineness) and cubed—and of concentrates given at either 2 or 4 kg per 10 kg milk. Hay averaged 18·2% of total forage DM intake with mean daily intakes of 1·28, 1·22 and 2·26 kg DM per cow in the long, short and ground forms respectively. The highest daily intakes of forage, i.e. silage plus hay, occurred on the ground hay treatments, with values of 10·24 and 9·25 kg DM per cow on the 2 and 4 kg concentrate treatments respectively. The mean daily milk yields were 18·2,18·2 and 19·2 kg per cow on the long, short and ground hay treatments respectively but the increase in yield with the ground hay was only significant at the low level of concentrate intake. The hay treatments had small and non-significant effects on milk composition. It is concluded that ground hay was superior to either long or chopped hay as a supplement for silage, but the small advantages depended on the level of concentrate intake.  相似文献   

20.
Agriculture's multifunctional role as provider of non-commodity outputs has received increased attention in the debate on the future of agricultural policy. To identify appropriate economic policies, a distinction must be made between concerns involving market failure and a consequent misallocation of resources, and those relating to distributional issues. We argue that it is essential to restrict the concept of multifunctionality to non-commodity outputs involving technical externalities or public goods and for which market failure and the misallocation of resources are important (e.g., amenity values and agricultural pollution). Other non-trade concerns, such as rural incomes and employment and food security, involve distributional issues, but no resource misallocation. This distinction makes it possible to identify different types of domestic policy measures to address them effectively and efficiently. Through reference to an empirical application to Taiwanese paddy rice policy, we illustrate that the most effective way to reconcile non-trade concerns is through policy measures that correct for market failure by valuing non-commodity outputs appropriately and a separate set of measures that address distributional issues.
David BlandfordEmail:
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