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21.

Purpose

The aim of this work was to improve the understanding of the spatial and temporal dynamics of suspended sediment transport during flushing flows in a large regulated river, the lower River Ebro (NE Spain).

Materials and methods

Relationships between sediment and discharge (i.e. discharge (Q)–suspended sediment concentrations (SSC)) were examined during six flushing flows using continuous discharge and turbidity records obtained at six monitoring sections distributed along the lower Ebro River for the 2008–2011 period.

Results and discussion

Analyses revealed marked spatial and temporal patterns. At the spatial scale, the Q–SSC relationships were mostly influenced by the different routing velocity of discharge and sediment waves. At the upstream sections, the sediment peak usually preceded peak discharge (i.e. clockwise loop); however, flow routing through the 85-km channel length tends to increase the lag between them, modifying the hysteresis towards counter-clockwise patterns in the downstream direction. At the temporal scale, the season when the artificial releases were performed strongly influenced the sediment availability, with similar-magnitude flushing flows generating higher sediment peaks in autumn than in spring.

Conclusions

These results are of great interest in order to reinforce the flushing flows programme in the lower Ebro River, so as to help achieve the sustainability of the riverine and deltaic ecosystems.  相似文献   
22.
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23.
The tolerance of different coffee-plant progenies to zinc (Zn) deficiency was studied in a green house experiment arranged in a completely randomized design, in a 14 × 2 factorial scheme (14 progenies and two Zn concentrations), with four replications. Coffee-plant seedlings were grown for ten months in nutritive solution with or without Zn. There were evaluated for growth characteristics, zinc concentrations, and zinc requirement. The grouping involving growth characteristics allowed discriminating the progeny ‘UFV 4066-3’ as highly zinc-demanding and ‘IAC 4376-5’ as low zinc-demanding. The data on plant dry matter and zinc accumulation showed that the progenies ‘IAC 4376-5’ and ‘UFV 4066-5’ had low zinc requirement when ‘Caturra Amarelo 1’, ‘UFV 4066-3’, ‘Caturra Amarelo 2’ and ‘Caturra Vermelho 2’ had high zinc requirement. Leaf area reduction (%), leaf number, active zinc content in completely expanded leaves and total zinc in roots were the variables of highest relative importance in discriminating coffee plant progenies.  相似文献   
24.
Native to the neotropics, the avocado seed moth Stenoma catenifer Walsingham (Lepidoptera: Elachistidae) is a specialist pest of the family Lauraceae and considered one of the most important pests of avocados worldwide. However, little is known regarding its spatial distribution within a single tree. Therefore, we designed a study to evaluate the effects of canopy height and aspect (i.e., side of the tree) on fruit infestation by S. catenifer larvae in avocados. The study was conducted in three commercial organic avocado orchards located in São Paulo, Brazil. At each orchard, 40 fruit from 30 random trees were sampled weekly from October 2017 through February 2018, evaluating the number of fruits infested by S. catenifer larvae at three tree heights (bottom, middle, and top). In addition, fruits on the ground were also sampled. We also evaluated the effect of the side of the tree where the fruits were collected, i.e., whether they were on the side facing the east (sunrise) or the west (sunset). Within the avocado canopy, the level of fruit infestation by S. catenifer larvae was significantly higher at the top of the trees than in the middle and bottom. Fruit on the ground had lower levels of infestation than those on the tree canopy. The level of fruit infestation was also higher on the side of avocado trees facing the east (sunrise). Understanding the within-tree distribution of S. catenifer will help to better target monitoring and control activities against this pest in avocados.  相似文献   
25.
Tomato leaves showing severe leaf spot symptoms have been observed and sampled in the central west and southwest Taiwan during 2015 and 2016. The symptoms were similar to those of bacterial leaf spot/late blight diseases, but only Stemphylium-like fungi were consistently isolated from the diseased tomato. Upon spray inoculation of tomato, Stemphylium-like isolates caused leaf spot symptoms identical to those of naturally infected plants, and the pathogenic isolates were successfully re-isolated from inoculated leaves. The tomato-pathogenic isolates were identified as S. lycopersici based on morphological characterization and molecular identification. S. lycopersici has been previously reported to cause gray leaf spot of tomato in the temperate regions, but the majority of S. lycopersici-caused lesions were black/dark brown rather than gray in our surveillance. Accordingly, it is suggested that S. lycopersici-caused disease of tomato is named Stemphylium leaf spot of tomato more appropriately than tomato gray leaf spot. Moreover, S. lycopersici-caused leaf spot disease on tomato has been distributed in major tomato production regions in Taiwan. The information provided by our study will be important for future breeding of tomato cultivars, especially for tomato producers in Taiwan.  相似文献   
26.
There are few reports on the pathogenesis of scrapie (Sc) and Visna/maedi virus (VMV) coinfections. The aim of this work was to study in vivo as well as post mortem both diseases in 91 sheep. Diagnosis of Sc and VMV infections allowed the distribution of animals into five groups according to the presence (+) or absence (−) of infection by Sc and VMV: Sc−/VMV−, Sc−/VMV+, Sc+/VMV− and Sc+/VMV+. The latter was divided into two subgroups, with and without VMV-induced lymphoid follicle hyperplasia (LFH), respectively. In both the lung and mammary gland, PrPSc deposits were found in the germinal center of hyperplasic lymphoid follicles in the subgroup of Sc+/VMV+ having VMV-induced LFH. This detection was always associated with (and likely preceded by) PrPSc observation in the corresponding lymph nodes. No PrPSc was found in other VMV-associated lesions. Animals suffering from scrapie had a statistically significantly lower mean age than the scrapie free animals at the time of death, with no apparent VMV influence. ARQ/ARQ genotype was the most abundant among the 91 ewes and the most frequent in scrapie-affected sheep. VMV infection does not seem to influence the scrapie risk group distribution among animals from the five groups established in this work. Altogether, these data indicate that certain VMV-induced lesions can favor PrPSc deposits in Sc non-target organs such as the lung and the mammary gland, making this coinfection an interesting field that warrants further research for a better comprehension of the pathogenesis of both diseases.  相似文献   
27.
Primiparous ewes and multiparous ewes show physiological differences during pregnancy, which can have an impact on the development of their offspring. The objective of this study was to compare the changes in the metabolic profile and in the size of some foetal bones throughout gestation between primiparous and multiparous ewes. Twelve primiparous (PM) ewes and 14 multiparous (MT) ewes were used. According to the dates of lambing, two groups of ewes were formed: Group 1 (G1, n = 6 PM and n = 7 MT) and Group 2 (G2, n = 6 PM and n = 7 MT). The body weight, body condition score, metabolic and foetal morphometric parameters were determined from before conception until the end of gestation. After lambing, the body weight and survival rate during the first 72 hr of life of lambs, as well as the maternal behaviour score were recorded. The PM ewes were lighter (p < .01) and had a greater mobilization of body reserves during gestation, mainly evidenced by a greater serum concentration of NEFAs and lower serum concentration of total proteins (p < .05) compared with the MT ewes. The parity did not affect the foetal morphometric variables. The lambs of MT ewes were heavier at parturition (p = .002) and tended to have a greater survival rate than those lambs of PM ewes (p = .09). In conclusion, PM ewes and MT ewes differ in their metabolic profile throughout the gestation. However, in the present study, we did not find parity differences in the dimensions of foetal bones during growth in gestation.  相似文献   
28.
Electroejaculation (EE) is a technique widely used to collect semen in ruminants, which produces a stress response with negative effects on animal welfare. The aim of this paper was to characterize the stress response during conventional EE in rams that have been frequently electroejaculated. Blood samples were collected since 20 min before and until 120 min after electroejaculating 10 rams. Electroejaculation affected hormone concentration, as cortisol increased, and testosterone decreased after EE. Heart and respiratory rate increased 10 min after EE. Several blood parameters, such as glycaemia, an increase in total protein and creatine kinase concentrations and a decrease in haematocrit, haemoglobin, red blood cell and alkaline phosphatase concentrations. The rams vocalized 13.8 ± 2.4 times, and the largest length of vocalizations during EE was associated with the numbers of pulses in which the rams ejaculated. In this paper, we provide a complete characterization of the stress response to EE in rams. We showed that although rams have been frequently electroejaculated, an important stress response including changes in respiratory rate, testosterone concentrations, haematological and biochemical parameters were observed, besides the changes in cortisol concentrations and heart rate, suggesting that rams were not habituated to EE. In addition, we described the main parameters of vocalizations and its relation with the moment of EE. The information displayed on the frequent use of EE in the rams should be considered in relation to the welfare implications.  相似文献   
29.
In this study, the distribution of eight allelochemicals among the foliage, roots, and seeds of different wheat varieties is reported for two different sampling campaigns, corresponding to two consecutive years. The determination of benzoxazinoid derivatives was performed by combining pressurized liquid extraction--solid-phase extraction followed by liquid chromatography--electrospray mass spectrometry. To the authors' knowledge, there are no previous works about the content of allelochemicals in seed tissue of germinated wheat seedlings. Allelochemicals found in seeds were detected at levels similar to those found in foliage and roots. The results showed that the type of metabolites detected depends strongly on the working up procedure of the plant material, as well as of plant growth stage. A general decrease of the total amount of allelochemical content in the plants was observed with plant age. There was a significant difference in the total amount of benzoxazinoid derivatives in the different wheat varieties analyzed.  相似文献   
30.
Maedi-Visna Virus (MVV) seroprevalence and its relationship with housing and mode of rearing of replacement ewe-lambs was investigated in 38 non-randomly selected sheep-flocks in Spain. They included extensive lamb-producing Manchega cross-bred flocks raised almost permanently at pasture, semi-intensive Latxa dairy flocks housed 2-8 months/year and intensively raised Assaf dairy flocks housed most time and at higher stocking density in less ventilated buildings than other flocks. Most flocks raised replacement lambs naturally with their dams until weaning and as a separate flock thereafter until lambing at one year of age. Seroprevalence (95% confidence intervals) was 77%, 25% and 5% (4-6) in intensive, semi-intensive and extensive flocks, respectively and the median (interquartile range) flock-seroprevalence was 82% (66-94) in intensive flocks, 31% (14-31) in semi-intensive flocks and 4% (0-7) in extensive flocks. Seroprevalence was lowest in one year-old sheep and increased to flock levels during the year after introduction into the adult flock in most intensive flocks and more gradually in other flocks. Adult flock seroprevalence was associated with housing time but this relationship was not evident within a particular rearing system, indicating that other unknown factors are critical in horizontal MVV-transmission. Low seroprevalence in extensive flocks further supports previous indications that lactogenic MVV-infection is relatively inefficient and horizontal transmission is necessary to ensure long-term maintenance of MVV and this could explain that MVV has not been reported from countries with mainly extensively reared sheep such as Australia and New Zealand. Moreover, it indicates that MVV-control in extensive and semi-intensive flocks can be simple and inexpensive.  相似文献   
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