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  • 1
    Electronic Resource
    Electronic Resource
    Weed populations in olive groves under non-tillage and conditions of rapid degradation of simazine (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 36 (1996), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In 49 olive tree groves in southern Spain under non-tillage and treated in the autumn with simazine, a total of 315 weed species was identified. However, only eight annual specics reached a moderate mean infestation of infested ficlds. In each field the number of observed species ranged from 4 to 78. The most important annual species that survived simazine treatment were Lolium rigidum, Galium tricornutum and Sherardia arvensis and, locally in a few fields, others such as Amaranthus spp., Conyza spp., Pulicaria paludosa, Sinapis alba. Torilis arvensis and Rumex bucephalophorus. Sedum album, R. bucephalophorus, P. paludosa, Briza maxima and Hypericum perforatum were mainly found in slope soils with high altitude and low carbon content. Cyperus rotundus, Conyza banariensi, Amaranthus blitoides, Galium spurium and Diplotaxis virgata were found at high densities in irrigated fields. Simazine residues recorded 6 months after herbicide application were very low, amounting on average to levels less than 3% of the applied rate. In soil treated with simazine for 7 years. simazine degradation was much faster than in previously untreated soil, particularly at temperatures of 15-25°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1996.tb01795.x
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  • 2
    Electronic Resource
    Electronic Resource
    Grassy weeds in winter cereals in southern Spain
    Amsterdam : Elsevier
    Crop Protection 8 (1989), S. 181-187 
    Details
    ISSN: 0261-2194
    Keywords: Spain ; Weeds, grassy ; cereals, winter
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0261-2194(89)90024-0
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  • 3
    Electronic Resource
    Electronic Resource
    Competition between Ridolfia segetum and sunflower (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 35 (1995), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Studies on competition between Ridolfia segetum Maris, and sunflower (Helianthemum annuus L.) were conducted at eight locations in southern Spain in 1990 and 1991. in order to define competition models and to estimate from these economic thresholds as affected by crop inputs and potential yields. Competition losses in sunflower crops ranged from 19% to 56% of weed–free yields. There were slightly better correlations between percentage sunflower reduction and weed density than with weed dry weight, (−0.66 and −0.59, respectively). The weed competitive index, or sunflower crop dry weight reduction per unit dry weight of R. segetum, was 1.09. The percentage yield losses due to weed density (NPRt) were fitted to multiple linear, quadratic, exponential and hyperbolic models. The hyperbolic equation, %RSY=100 (1+1/b*NPRt)−1, where b=0.14 and is the R. segetum competitive ability index, had the lowest error sum of squares (SSE), and gave the best biological explanation for the competition response. Early emergence (before mid–March) made weeds about 1.5 times more competitive than late emergence. The economic threshold to offset the cost of a shallow post–emergence tillage, assuming 70% control efficiency, ranged from about 2.5 plants m −2 for low–yielding crops(1200kgha−1) to less than one plant m−2 for higher–yielding crops (2800 kg ha−1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1995.tb01632.x
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of environmental factors on the weed flora in crops in the Guadalquivir Valley (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 30 (1990), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The study was conducted on the weed flora of the main irrigated crops of the Guadalquivir Valley. The TWINSPAN (Two Way Indicator Species Analysis) method was applied for each crop separately to all the species present as well as to their degree of infestation. The results indicated that soil texture may markedly influence the flora, whereas the effects of pH and carbonate content were less important. The climatic differences found in the three areas studied were of little importance. The type of irrigation markedly influenced the flora, although it was always related to edaphic factors, especially texture and slope.In general, the weed flora found in the crops can be divided into two communities. One is characterized by species such as Ridolfia segetum, Picris echioides, Phalaris brachystachys, Phalaris paradoxa and Chrozophora tinctoria and the second by Capsella bursa-pastoris, Cyperus rotundus, Paspalum paspalodes, Digitaria sanguinalis, Sorghum halepense and Portulaca oleracea. The first community comprises weeds in the higher altitudes, further away from the riverbed, with a soil of clayey texture, a high slope and irrigated with sprinklers. The second community comprises the flora of flat areas, with sandy soils, located in the middle and low river terraces and furrow irrigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1990.tb01723.x
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  • 5
    Electronic Resource
    Electronic Resource
    Weed flora in the Middle Valley of the Guadalquivir, Spain (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 29 (1989), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A floristic study of the weeds in irrigated crops in the Guadalquivir River Valley (southern Spain) revealed a total of 284 species in the 267 fields surveyed, of which about 100 can be considered highly harmful. The families with the highest numbers of species were Compositae, Gramineae, Leguminosae, Cruciferae and Umbelliferae. Although 77·8% of the species were therophytes, geophytes were important in spring-sown crops. Most species were of Mediterranean origin, especially in autumn-sown crops; Cosmopolitan and Neotropical species were more important in the spring-sown crops. At the early and late crop growth stages 7% and 10%, respectively, of the fields had severe or very severe infestations.The relationships between the main weed species and crops were studied by cluster analysis, using the corrected frequency of each species in each crop as the reference parameter. This allowed classification of the species into subgroups and hierarchical groups according to their agro-ecological preferences. A close relationship was found between a given crop, its cycle and the usual soil management practices and the phenology of certain species, reflecting the influence of these factors in restricting the germination period. The analysis differentiated the typically winter, summer and intermediate weed floras.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1989.tb00857.x
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  • 6
    Electronic Resource
    Electronic Resource
    Weed flora of dryland crops in the Córdoba region (Spain) (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 30 (1990), S. 0 
    Details
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In a study of the weed flora of dryland crops in the Córdoba region (southern Spain) in 1983 and 1984, a total of 256 species from 41 families was identified in the 201 fields surveyed. The families with the highest numbers of species were Compositae, Gramineae, Leguminosae and Cruciferae. Therophytes represented 79% of the biological spectrum, with hemicryptophytes and geophytes more especially in the spring-sown crops. At the early and late crop growth stages about 4% and 8%, respectively, of the fields had severe or very severe infestations. The seasonality of the crop had a marked influence on the weed flora, mainly due to the relationship of its phenological cycle with well defined climatic periods and to soil management practices. Cluster analysis clearly differentiated typically autumn-spring and spring-summer floras as well as a set of common species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3180.1990.tb01718.x
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  • 7
    Electronic Resource
    Electronic Resource
    Far-red light inhibits growth but promotes carotenoid accumulation in the green microalga Dunaliella bardawil (1996)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 98 (1996), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: It has been demonstrated that far-red light reduces growth of marine phytoplankton and that light quality controls growth and photosynthetic metabolism in algae. The green halotolerant microalga, Dunaliella bardawil, accumulates high amounts of β-carotene (up to 10% of its dry weight) under conditions of high light or nutrient limitation. The influence of increasing irradiance and of far-red light in D. bardawil was studied. Continuous irradiance was provided by white fluorescent lamps alone (WL) or supplemented with far-red Linestra lamps (WL+FR). For both types of light, cultures were acclimatized at increasing irradiances (50-300 µmol m−2 s−1), and cell density, photosynthetic activity and pigment content were determined. Cell density increased with the photon irradiance, and was higher in WL than in WL+FR under the same irradiance, but the reverse occurred in respect of cell volume. Growth rate was higher under WL+FR. Far-red light induced faster growth but reduced the maximal cell density of the cultures. Chlorophyll a concentration was higher in white light, but total carotenoid content increased dramatically in both far-red light treatments (about 50% on a per cell basis) and with the increase of irradiance. Our results show that far-red light has a significant influence on growth and photosynthesis of D. bardawil, inducing a decrease in cell density, photosynthetic activity and chlorophyll concentration, and an increase in growth rate, cell volume and carotenoid content.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1996.980226.x
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  • 8
    Electronic Resource
    Electronic Resource
    Spatial distribution of antisymmetrically-curved extragalactic radio-jets (1990)
    Springer
    Astrophysics and space science 164 (1990), S. 131-137 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In order to fine the observational restrictions for theoretical models explaining curvatures of extragalactic jets, tails, or lobes, a list of 365 objects has been extracted from published data. Radio sources exhibiting both jets curved in the same direction (called typeV) are equally frequent as those exhibiting them with opposite directions. Among the last antisymmetric types, two possibilities are considered: when jets draw a clockwise (typeS) or counterclockwise (typeN) image. TypesS andN are not only equally frequent as expected, but they do not have preferred locations in the sky. At least at large scales, once a jet is thrown out, it has an equal chance to be sent in any direction, independently of the one followed by its twin counterjet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653558
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  • 9
    Electronic Resource
    Electronic Resource
    The magnetic fields in M31, NGC 7331, NGC 2841, NGC 6946, and our galaxy (1989)
    Springer
    Astrophysics and space science 156 (1989), S. 189-194 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A time-independent model for the radial distributions of gas and magnetic field has been applied to the galaxies Milky Way, M31, NGC 7331, and NGC 2841, in order to explain the gaseous ring patterns in spiral galaxies, and to NGC 6946 to see if this model is valid for galaxies without a gaseous ring. The model takes the gas pressure as its input data and solves the MHD equations to calculate the magnetic field responsible for the gas distribution. This field has an azimuthal component only, and can be used to predict synchrotron radio emission. A discussion about the dependence of the synchrotron radiation profiles obtained upon the assumed relationN 0(ϱ,B) for the cosmic-ray density per unit energy as a function of gas density and field strength, is here considered in detail. It is shown that a relation of the typeN 0∼ϱ/B, which takes into account the loss of energy of the cosmic-relativistic electrons, yields good agreement with the observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646364
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  • 10
    Electronic Resource
    Electronic Resource
    Statistical study of optical galactic warps (1990)
    Springer
    Astrophysics and space science 171 (1990), S. 239-241 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A list of northern spiral NGC galaxies, with inclinations higher than 74°, and exhibiting warps have been obtained from the Palomar Sky Survey (POSS). Approximate position angles and ‘warping angles’ are given for each galaxy, in order to have a first reference for statistical studies of the warping phenomenon. When we take into account that warps are not always observed (depending on their relative position with respect to the observer) the resulting frequency of warps was so high that a tentative conclusion is that all disks are warped.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00646856
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