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11.
Yasser Trabelsi Foued Gharbi Abdessalem El Ghali Mansour Oueslati Mohammad Samaali Wahid Abdelli Souad Baccouche Malik Ben Tekaya Moncef Benmansour Lionel Mabit Nabiha Ben M’Barek Nafaa Reguigui Jose M. Abril 《Journal of Soils and Sediments》2012,12(5):784-796
Purpose
Ichkeul National Park, NW Tunisia, is a UNESCO Biosphere Reserve. Garaet El Ichkeul Lake is known for its seasonal variability in water level and salinity. In recent decades, the waterbody has been affected by the construction of new hydraulic structures. To reduce the impacts of dams and to maintain the sustainability of the ecosystem, a sluice was built at the outlet of the lake, and it operated for the first time in 1996. This paper describes an investigation of recent sedimentation dynamics in Ichkeul Lake, determined by radiometric dating of sediment cores.Materials and methods
A sediment core was collected with a UWITEC gravity corer at the deepest, central part of the lake in August 2009. Specific activities of unsupported lead-210 (210Pb) and caesium-137 (137Cs) were measured in the core, enabling calculation of recent sediment accumulation rates (SAR). Published radiometric data from nearby sediment cores, collected in 1997 and 1982, provide a comparison.Results and discussion
The measured excess 210Pb inventory was 5300?±?500?Bq?m?2, leading to an estimation of constant flux of 165?±?16?Bq?m?2?yr?1, a value higher than the best estimate for local atmospheric fluxes (123?±?12?Bq?m?2?yr?1) and the flux estimated from the core collected in 1982 (48?Bq?m?2?yr?1). The 137Cs inventory was 3550?±?120?Bq?m?2, two times higher than the historical 137Cs atmospheric deposition in the area. The 137Cs profile displayed a distinct peak, but the 137Cs depth-distribution did not follow the pattern expected from atmospheric deposition. Application of the constant rate of supply (CRS) model, with the reference point method, produced a chronology and SAR values comparable to those found in previous work. The whole 137Cs profile was quantitatively reconstructed from the historical records of atmospheric deposition, using the system-time-averaged (STA) model.Conclusions
The CRS and STA models provide consistent sediment accumulation results for the whole data set, considering the time resolution of the chronology (~6?years) and analytical uncertainties. Results from cores sampled in 1982, 1997 and 2009 reveal an increasing SAR trend, from ~0.25?g?cm?2?yr?1 in the early 1940s to ~0.67?g?cm?2?yr?1 at present. In the 13?years since installation of sluice gates at Tinja, SAR in the central Ichkeul Lake has not declined. Thus, if siltation continues at the present rate, shallowing of the lake will seriously affect the hydromorphology and ecology of this important lake. 相似文献12.
Kalthoum Harbaoui Theo van der Lee Vivianne G. A. A. Vleeshouwers Nouri Khammassy Moncef Harrabi Walid Hamada 《Potato Research》2013,56(1):11-29
Severe late blight epidemics in Tunisia in recent years prompted population studies on the pathogen responsible for this disease, Phythophthora infestans. Characterisation of 165 Tunisian P. infestans isolates collected from 2006 to 2008 was performed for the mating type and mt haplotype, while subsets were analysed for metalaxyl sensitivity (n?=?65), virulence on differential set of 11 R genes of Solanum demissum (n?=?31), aggressiveness on cv. Bintje (n?=?36) and measurement of the radial growth on agar medium at three temperatures (n?=?38). Most isolates from potato and all isolates from tomato had the A1 mating type. The A2 mating type was detected in the north-east and northern areas, but not in the north-west. All the A2 mating type isolates were metalaxyl resistant and seem to be part of a new generation of the P. infestans isolates which are more aggressive, with more complex races, and tolerant to higher temperatures. The increased severity of epidemics during 2006 to 2008 can be attributed to favourable weather conditions during growing seasons, adaptation of new genotypes, widespread phenylamide resistance in potato production regions and most probably incorrect spray programmes. In contrast to the presence of complex pathotypes in two major potato crop regions (north-east and northern areas), the P. infestans population detected in the other regions and in tomato crops was still relatively simple. Compared with the situation in Europe and the American continent, or even compared with neighbouring countries such as Algeria, the genetic changes in Tunisia are still comforting and require strict management decision on late blight control to avoid the spread of new P. infestans populations from Europe or neighbouring countries. 相似文献
13.
Lobna Ben Mohamed Mohamed Cherif Moncef Harrabi Rex F. Galbraith Richard N. Strange 《European journal of plant pathology / European Foundation for Plant Pathology》2010,126(3):293-303
Five chickpea cultivars, Chitoui, Neyer, Kasseb, Beja 1 and Bouchra, were planted on three sowing dates at two Experimental
Stations in Tunisia: Bou Salem in the north and the more southerly Mornag, where the climate is drier. Severity of blight,
caused by Ascochyta rabiei, was measured on a 1–9 scale (defined) on vegetative parts and on pods as percent infected and percent infected that were
empty. At both locations, disease was essentially absent on plants sown on the third dates but present on plants sown on the
two earlier dates. At Bou Salem, disease severity was highest for the second sowing date whereas at Mornag it was highest
for the first sowing date; but for each sowing date, disease severity was lower at Mornag than at Bou Salem. Yield components
were measured as number of pods per plant, number of seeds per plant, number of seeds per 100 pods, 100 seed weight and weight
of seeds per plant. Both disease severity and yield differed significantly among sowing dates (differently at each location)
and also among cultivars for each sowing date, these differences depending both on sowing date and location. A lower yield
was always associated with a higher disease severity, although the quantitative relationship differed between cultivars and
locations. Cultivar Beja 1 had the lowest vegetative disease scores at both locations and both sowing dates 1 and 2. Beja 1
also scored well for all yield components. Plants sown on the third (latest) date gave the highest yields for all cultivars
at both locations (except for an unusually high yield of Neyer at Mornag on sowing date 2), in some instances being more than
double those from the earlier sowing dates. Thus, in contrast to other studies, late sowing did not result in yield loss. 相似文献
14.
Ahmed Barkia Ali Bougatef Rim Nasri Emna Fetoui Rafik Balti Moncef Nasri 《Fish physiology and biochemistry》2010,36(4):893-902
Trypsin from the viscera of Bogue (Boops boops) was purified to homogeneity by precipitation with ammonium sulphate, Sephadex G-100 gel filtration and Mono Q-Sepharose
anion exchange chromatography, with an 8.5-fold increase in specific activity and 36% recovery. The molecular weight of the
purified enzyme was estimated to be 23 kDa by SDS–PAGE and size exclusion chromatography. The purified trypsin appeared as
a single band on native-PAGE and zymography staining. The purified enzyme showed esterase-specific activity on N-α-benzoyl-l-arginine ethyl ester (BAEE) and amidase activity on N-α-benzoyl-dl-arginine-p-nitroanilide (BAPNA). The optimum pH and temperature for the enzyme activity, after 10 min incubation, were pH 9.0 and 55°C,
respectively, using BAPNA as a substrate. The trypsin kinetic constants K
m and k
cat on BAPNA were 0.13 mM and 1.56 s−1, respectively, while the catalytic efficiency k
cat
/K
m was 12 s−1 mM−1. Biochemical characterisation of B. boops trypsin showed that this enzyme can be used as a possible biotechnological tool in the fish processing and food industries. 相似文献
15.
Cavaliere B De Nino A Hayet F Lazez A Macchione B Moncef C Perri E Sindona G Tagarelli A 《Journal of agricultural and food chemistry》2007,55(4):1454-1462
The selection of suitable markers from the secondary metabolism of lipoxygenase, in experimental olive oils produced from drupes harvested in different areas of the Italian Calabria region and of Tunisia, allows an easy discrimination between each cluster of samples. The origin of the foodstuff can be ascertained even when the distances between the production zones are very close to each other as in Calabria. Olive oils produced from irrigated and nonirrigated farms in Tunisia were also clearly distinguishable. The markers were detected by chemical ionization mass spectrometry with an ion trap gas chromatography-mass spectrometry apparatus. The quantitative data of Calabrian olive oil samples were subjected to linear discriminant analysis, whereas the Tunisian data were treated by means of other two statistical tools, i.e., the Kruskal-Wallis test and the Wald-Wolfowitz test. 相似文献
16.
17.
Chiraz Charfi Masmoudi Moncef Masmoudi Jihène Abid-Karray Nétij Ben Mechlia 《Scientia Horticulturae》2011
Measurements of sap flux were carried out from May 2003 to March 2004 on 6 year-old irrigated olive trees of cultivar Chétoui cultivated at 6 m × 6 m spacing in Mornag (36.5°N, 10.2°E), Northern Tunisia. The aim of the research is to evaluate the sap flux technique for its applicability with young olive trees and to estimate their water consumption under field conditions. Three thermal sensors were implanted in the trunk of three olive trees following to North (N), South-East (SE) and South-West (SW) directions. Data were analyzed following to the procedure of Do and Rocheteau (2002b) that derives from Granier (1985). In this paper, data on probe calibration, wood conductive section estimation and sap flux spatial-variability are presented and discussed. Relationships between sap flux measurements, climate and soil water status have been investigated. Results show that sap flux values vary with sensor position, soil water content and climate demand. Good agreements between sap fluxes and global radiation and reference evapotranspiration measurements were observed. Some variations were recorded under water shortage conditions. Maximum and minimum daily fluxes of 4.5 l and 41.0 l per tree were found in February 2003 and in August 2003, respectively. Maximum transpiration represented only 53% of the crop evapotranspiration as determined by the F.A.O. method. 相似文献
18.
Intidhar Bkhairia Naourez Ktari Islem Younes Maher Kammoun Moncef Nasri Sofiane Ghorbel 《Journal Of Aquatic Food Product Technology》2013,22(6):597-613
Digestive alkaline proteinases from golden grey mullet (Liza aurata) were extracted and characterized. The crude alkaline protease showed optimum activity at pH 8.0 and 60°C, and it was highly stable over a wide range of pH from 4.0 to 10.0, retaining more than 80% activity after incubation for 1 h at 4°C. The alkaline proteases showed extreme stability toward nonionic and anionic surfactants after preincubation for 1 h at 25°C and relative stability toward oxidizing agents. Additionally, the crude enzyme showed excellent stability and compatibility with various solid and liquid detergents. Further, proteases from golden grey mullet viscera were found to be effective in the deproteinization of shrimp wastes. The protein removal after 3 h at 45°C with an enzyme/substrate (E/S) ratio of 10 U/mg protein was about 76%. The golden grey mullet proteases were also shown to be efficient in the production of antioxidant protein hydrolysate. 相似文献
19.
Naourez Ktari Hayet Ben Khaled Imen Lassoued Sofiane Ghorbel Moncef Nasri 《Journal Of Aquatic Food Product Technology》2013,22(3):208-220
Carboxypeptidase B (CPB) from zebra blenny (Salaria basilisca) viscera was purified using ammonium sulphate precipitation and Sephadex G-100 gel filtration, with a 28-fold increase in specific activity and 21.72% recovery. The molecular weight of the enzyme was estimated to be 34.5 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). The optimum pH and temperature for the enzyme activity were around pH 8.0 and 60°C, respectively, using Hippuryl-l-Arg as a substrate. The enzyme was unstable above 50°C and below pH 5.0. The enzyme was activated by Co2+ and Zn2+ and inhibited by ethylenediaminetetraacetic acid (EDTA). The N-terminal amino acid sequence of the enzyme was determined as S P S Y T K Y N T. The CPB kinetic constants, Km and kcat for Hippuryl-l-Arg, were 0.32 mM and 36.23 s?1, respectively. 相似文献
20.