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  • 1
    ISSN: 1432-0789
    Keywords: Key words Genetic variability ; Vigna unguiculata ; Nitrogen-15 method ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  N fixed in 16 cultivars of cowpea [Vigna unguiculata (L.) Walp] inoculated with effective Bradyrhizobium strains collected from the West African MIRCEN culture collection was measured by 15N isotope dilution technique. In all plant parts, significant differences in the percentage of N derived from the atmosphere (%Ndfa) and the amount of Ndfa occurred between the cultivars. Ndoute variety exhibited the highest %Ndfa (74.33% in shoots; 60.90% in roots) and accumulated more fixed N (960 mg N plant–1 and 38 mg N plant–1 in shoots and roots, respectively). Therefore this cultivar should be selected as the highest N-fixing cowpea cultivar. It also should be used in a breeding programme to contribute to the development of cultivars that could stimulate an intensive use of cowpea in many different cropping systems in Africa with a view to maintaining soil fertility.
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  • 2
    ISSN: 1432-1890
    Keywords: Keywords Glomales ; Soil depth ; Faidherbia albida
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Five arbuscular mycorrhizal (AM) fungal species were isolated and propagated from surface and deep rhizospheres of Faidherbia albida trees growing in two ecoclimatic zones of West Africa: the semi-arid Sahelian and the more humid Sudano-Guinean areas. Of these species, Glomus aggregatum, Glomus caledonium, and Glomus mosseae were trapped by F. albida roots when cultivated with either surface or deep soils. Glomus fasciculatum was found exclusively at the semi-arid Sahelian sites of Louga and Diokoul and Gigaspora margarita was isolated only from 16.5-m and 34-m-deep samples. Comparable glomalean fungal species richness was identified in deep (1.5–34 m) and surface (0.15 m) samples. The isolation and the propagation of glomalean fungi from F. albida rhizospheres confirmed the presence of viable AM fungal propagules, down to the water table, as deep as 34 m.
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  • 3
    ISSN: 1573-5036
    Keywords: Acacia raddiana ; Acacia senegal ; Acacia seyal ; Faidherbia albida ; isotope dilution ; 15N ; nitrogen fixation ; Parkia biglobosa reference tree ; Tamarindus indica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted in a greenhouse using the 15N isotope dilution method and two reference plants, Parkia biglobosa and Tamarindus indica to estimate nitrogen fixed in four Acacia species: A raddiana, A. senegal, A. seyal and Faidherbia albida (synonym Acacia albida). For the reference plants, the 15N enrichments in leaves, stems and roots were similar. With the fixing plants, leaves and stems had similar 15N enrichments; they were higher than the 15N enrichment of roots. The amounts of nitrogen fixed at 5 months after planting were similar using either reference plant. Estimates of the percentage of N derived from fixation (%Ndfa) for the above ground parts, in contrast to %Ndfa in roots, were similar to those for the whole plant. However, none of the individual plant parts estimated accurately total N fixed in the whole plant, and excluding the roots resulted in at least 30% underestimation of the amounts of N fixed. Between species, differences in N2 fixation were observed, both for %Ndfa and total N fixed. For %Ndfa, the best were A. seyal (average, 63%) and A. raddiana (average, 62%), being at least twice the %Ndfa in A. senegal and F. albida. Because of its very high N content, A. seyal was clearly the best in total N fixed, fixing 1.62 g N plant−1 compared to an average of 0.48 g N plant−1 for the other Acacia species. Our results show the wide variability existing between Acacia species in terms of both %Ndfa and total N fixed: A. seyal was classified as having a high N2 fixing potential (NFP) while the other Acacia species had a low NFP.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    World journal of microbiology and biotechnology 14 (1997), S. 177-184 
    ISSN: 1573-0972
    Keywords: Bradyrhizobium ; determinate ; indeterminate ; infection thread ; nodule ; Voandzeia subterranea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The infection of Vigna subterranea (formerly Voandzeia subterranea) by Bradyrhizobium strain MAO 113 (isolated from V. subterranea) was examined by light and transmission electron microscopy. Bacteria accumulated on the epidermis close to root hairs, and subsequently entered the latter via infection threads. Most of the steps involved in nodule formation were generally characteristic of determinate nodules, such as those which form on the closely related V. radiata. For example, nodule meristems were induced beneath the root epidermis adjacent to infected root hairs, but prior to infection of the meristem by rhizobia. Moreover, after the infection of some of the meristematic cells by the infection threads, and the release of the rhizobia into membrane-bound vesicles, the infection process ceased and dissemination of the rhizobia was by division of already-infected host cells. However, there were some aspects of this process in V. subterranea which have been more commonly described in indeterminate nodules. These include long infection threads entering a number of cells within the meristems simultaneously and a matrix within infection threads which was strongly labelled with immunogold monoclonal antibodies, MAC236 and MAC265, which recognize epitopes on an intercellular glycoprotein. The MAC236 and MAC265 antibodies also recognized material in the unwalled infection droplets surrounding bacteria which were newly-released from the infection threads. The amount of labelling shown was more characteristic of the long infection threads seen in indeterminate nodules such as pea (Pisum sativum) and Neptunia plena. The structure of mature V. subterranea nodules was similar to that described for other determinate nodules such as Glycine max, Vigna unguiculata and V.radiata, i.e. they were spherical and the infected zone consisted of both infected and uninfected cells. Surrounding the infected tissue was an inner cortex of uninfected cell layers containing the putative components of an oxygen diffusion barrier (including glycoprotein-occluded intercellular spaces), and an outer cortex with cells containing calcium oxalate crystals.
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  • 5
    ISSN: 1573-0972
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Résumé On a inoculéV. unguiculata poussant dans un sol Dek stérile avecRhizobium etRhizobium plusGlomus mosseae. On a recherché la réponse de la plante-hôte à ces deux traitements en estimant périodiquement les poids des nodules et des parties aériennes de la plante, la fixation d'azote (activité réductrice de C2H2), les teneurs en N et P jusqu'au 50e jour du cycle de végétation. C'est seulement au 45e jour après la plantation que le poids sec des parties aériennes des plantes inoculées avec deux symbiotes (plantes doublement inoculées) diffère significativement de celui des plantes inoculées avec Rhizobium seul. Le poids sec des nodules et la fixation N2 des plantes doublement inoculées sont significativement plus élevés que ceux des plantes inoculées avecRhizobium seul au 20e jour après la plantation mais il n'y a pas de différence significative pour la teneur en N (%). Pendant les 20 premiers jours, la teneur en P (%) des parties aériennes des deux catégories de plantes décroit progressivement; la teneur en P des plantes doublement inoculées est plus faible que celle des plantes inoculées seulement avecRhizobium. Plus tard, la teneur en P des plantes doublement inoculées augmente rapidement tandis que celle des autres plantes reste constante. L'accroissement du poids sec des nodules, de la fixation d'azote et de la teneur en P observé chez les plantes doublement inoculées correspond au démarrage du développement des hyphes extra-radicales deGlomus mosseae dans la rhizosphère.
    Abstract: Resumen Se cultivóVigna unguiculata cv. 58–185 en un suelo estéril tipo Dek, se inoculó conRhizobium sp. o conRhizobium sp. másGlomus mosseae. La respuesta de la planta huésped a los tratamientos se estudió midiendo periodicamente el peso seco de la parte aerea y de los nódulos, la fijación de N (actividad reductora de C2H2) y los contenidos de N y P hasta el 50° día del ciclo de crecimiento. La diferencia entre el peso seco de la parte aerea de las plantas con doble inoculación y aquellas inoculadas conRhizobium sp. unicamente, no fue significativa hasta 45 días despúés de la siembra. A los 20 días de la siembra tanto el peso seco de los nódulos como la fijación de nitrógeno de las plantas con doble inoculación eran significativamente superiores a los valores obtenidos para las plantas con soloRhizobium sp., aunque no se observaron diferencias en el contenido en N (%). Durante los primeros 20 días del ciclo el contenido en P (%) de ambos grupos de plantas disminuyó progresivamente, siendo los valores obtenidos por las plantas con doble inoculación inferiores a los de las demás. Más tarde el contenido en P de las plantas con doble inoculación aumentó rapidamente manteniéndose constante el de las demás. El incremento en el peso seco de los nódulos, en la fijación de N y en el contenido en P de las plantas con doble inoculación se correspondió con el inicio del desarrollo de las hifas extraradiculares deGlomus mosseae.
    Notes: Summary Vigna unguiculata cv. 58–185 grown in a sterile Dek soil was inoculated withRhizobium sp. orRhizobium sp. plusGlomus mosseae. Response of the host plant to the treatments was estimated by periodic measurements of shoot and nodule dry weights, N2 fixation (C2H2 reduction activity) and N and P contents up to the 50th day of the growth cycle. It was only 45 days after planting that shoot dry weight of dually inoculated plants differed significantly from that of plants inoculated withRhizobium sp. alone. Nodule dry weight and N2 fixation of dually inoculated plants were significantly higher than those of plants inoculated withRhizobium sp. alone from day 20 after planting, but there was no significant difference in N content (%). During the first 20 days, shoot P content (%) of both sets of plants decreased progressively, P content of dually inoculated plants being lower than that of the others. Later, P content of dually inoculated plants increased rapidly whereas P content of the other plants remained constant. Increase in nodule dry weight, N2 fixation and P content of dually inoculated plants corresponded to the onset of the development of the extra-radical hyphae ofGlomus mosseae. In the rhizosphere.
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  • 6
    Publication Date: 2008-05-29
    Description: New structural, metamorphic, finite-strain analysis and kinematic data from the southern part of the Mauritanides in Senegal (Bakel area) have revealed a history reflecting different tectonic regimes. The structural framework is expressed in the form of shear-zone systems comprising rectilinear NE-SW trending thrusts and NE-SW-trending ductile sinistral strike-slip faults associated with north-south- to NE-SW-trending transpression belts. The analysis of ductile fabrics reveals the presence of lineation trajectories that show a change from a tangential deformation towards the marginal zones in the Northern and Southern Domains of the belt to sinistral oblique transpression in the Central Domain. The deformation within the belt is strongly partitioned into shear zones distributed across the belt defining structural domains with accompanying large-scale folds and thrusts. This exemplifies wrench-style tectonics dominated by crustal-scale strike-slip shear zones in the orogen core and temporal and spatial progression outwards to the marginal zones. Thus, the Variscan orogeny in the southern part of the Mauritanides belt in Senegal developed through sinistrally oblique transpressive shearing along the borders of the orogen core leading to the exhumation of ultramafic rocks between large shear zones.
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  • 7
  • 8
    Publication Date: 2015-07-20
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 9
    Publication Date: 2014-08-11
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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  • 10
    Publication Date: 2014-03-20
    Description: The Paleoproterozoic Mako Belt in eastern Senegal is characterised by gold-bearing quartz veins. These are superimposed on the regional Birimian structural complex consisting of volcano-sedimentary and intrusive rocks in an Early Proterozoic greenstone belt. In the Mako Belt the multi-stage deformed quartz veins and hydrothermally altered protoliths are characterised by distinctive microstructures and CL properties. The high-grade Au-bearing quartz veins contain one or more generations of hydrothermal quartz. Brecciation of the veins is indicated by cemented fragments of zoned quartz. Gold in the mineralised zones occurs either as inclusions in pyrite or as native gold. Mineralisation typically occurs in vein systems which are brecciated, laminated, and/or show crack-seal textures. Microstructures indicate syn- to late-tectonic mineralisation. Au-mineralised veins contain quartz, carbonate, muscovite, fuchsite, tourmaline, and chlorite. Fluid inclusion studies reveal early, highly saline aqueous inclusions followed by main-stage aqueous-carbonic inclusions of low salinity and finally aqueous low-salinity inclusions. Petrographic observation and microthermometric data suggest that fluid inclusions in main stage quartz were trapped after phase separation from a heterogeneous H 2 O-CO 2 fluid. Gold deposition occurs over a temperature range of 220 to 320°C and pressures of 1.4 to 2.75 kbar (~5 to 10 km depth). The late-stage quartz carbonate vein corresponds to pressures of 0.75 to 1.25 kbar and depths of 3.0 to 4.5 km. A fluid pressure drop due to fracture failure is likely to have triggered Au precipitation. The Mako Belt Au deposits are comparable to a large number of orogenic lode gold deposits in the West African Craton.
    Print ISSN: 1012-0750
    Topics: Geosciences
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