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  • 1
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 217 (1999), S. 183-193 
    ISSN: 1573-5036
    Keywords: Image analysis ; minirhizotron ; roots ; soil type ; sugarbeet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Minirhizotrons speed up research on root demography, but image quality often hampers standardization of the image processing method. A simple procedure working on the blue band of colour images was tested on fibrous roots of sugarbeet (Beta vulgaris var. saccharifera). With respect to green and red, the blue band allows better detection of roots when their luminance is very similar to that of the background. The method makes use of an exponential algorithm of contrast stretching, which takes luminance frequency distribution into account. Based on a single threshold level, the procedure includes skeletonization. A minimum segment length was adopted to discriminate roots from extraneous objects. Although a specific minimum root length (MRL) value was calculated for each soil type, results show that a single value can be applied, indicating that this method can be profitably used for processing large samples of images.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 32 (1992), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Qualitative and quantitative surveys (biological and ecophysiological spectrum, structural organization, seed bank size) of the potential flora (PF) in maize (Zea mays L.) fields of the Po Valley are reported. Data were collected from 45 sites and two sampling depths (0–20 cm and 21–40 cm). Soil seed content was highly variable, ranging from 1660 to 53371 seeds m−2, with an average value of 10391 seeds m−2 and a median of 5500 seeds m−2. Seed stock was lower than 2000 seeds m−2 in 6.6% of the sites and over 10000 in 26.6%. Six species were found in more than 50% of the sites, representing 27.7% of the total stock: Anagallis arvensis L., Chenopodium album L., Stellaria media (L.) Vill., Echinochloa crus-galli (L.) P. Beauv., Amaranthus spp., Polygonum persicaria L. + P. lapathifolium 〉 L. Overall, 63 species were recorded, the species number per site ranging from 4 to 25, with a median value of 11. Therophytes accounted for 90.6% of the species and 94.3% of individuals. Of the species, 39.8% were assignable to the summer, 21.9% to the spring, 8.1% to the winter and 5.3% to the autumn germinating group, and 24.9% were non-seasonal. Simpson's dominance index for PF ranged from 0.11 to 0.525, with an average value of 0.21 and a median of 0.195. The Shannon diversity index had a range of 1.15–2.43, with an average value of 1.93 and a median of 1.91. In some cases (13.3%) compensation phenomena are evident, sustained by different species from site to site. These results form the basis of a discussion on the effectiveness and the limits of management strategies designed to reduce soil seed stock. Un profil de la flore potentielle des champs de mais de la Vallee du Pô Des enquêtes quali-quantitatives (spectre biologique et ecophysiologique, organisation structurale, taille du stock grainier) de la flore potentielle (FP) dans les champs de maïs (Zea mays L.) de la vallée du Pô, sont rapportées. Les données ont été collectées dans 45 sites à 2 profondeurs d'échantillonage (0–20 cm et 21–40 cm). La teneur en graines du sol était fortement variable, allant de 1660 à 53371 graines m−2 pour une moyenne de 10391 et une médiane de 5500. Le stock grainier était inférieur à 2000 graines m−2 dans 6,6% des sites et supérieur à 10000 dans 26,6%. 6 espèces ont été trouvées dans plus de la moitié des sites, représentant 27,7% du stock total: Anagallis arvensis L., Chenopodium album L., Stellaria media (L.) Vill., Echinochloa crus-galli (L.) P. Beauv., Amaranthus spp., Polygonum persicaria L., +P. lapathifolium L. Globalement, 63 espèces ont été inventoriées, avec le nombre d'espèces par site allant de 4 à 25 avec une médiane de 11. Le groupe biologique des therophytes concernait 90,6% des espèces et 94,3% des individus. Au sein des espèces, 39,8%étaient estivales, 24,9% indifférentes, 21,9% des printanières, 8,1% hivernales et 5,3% automnales. L'index de dominance de Simpson pour PF allait de 0,11 à 0,525 avec une moyenne de 0,21 et une médiane de 0,195. L'index de diversité de Shannon allait de 1,15 à 2,43 avec une moyenne de 1,93 et une mediane de 1,91. Dans quelques cas (13,3%) les phenomenes de compensation sont évidents, alimentés par différentes espèces d'un site à l'autre. Ces résultats forment la base d'une discussion sur l'efficacité et les limites des stratégies en vue de réduire le stock grainier du sol. Potentielle Flora in Maisfeldern der Po-Ebene Bei einer sowohl qualitativen als auch quantitativen Aufnahme der potentiellen Verunkrau-tung von Mais-(Zea-mays-)Feldern der Po-Ebene wurden Daten über das biologische und ökophysiologische Spektrum, die Struktur und den Umfang des Samenvorrats im Boden in 0–20 und 21–40 cm Tiefe an 45 Orten erhoben. Der Samenvorrat variierte erheblich und reichte von 1660 bis 53371 Samen m2 bei einem Mittelwert von 10391 und einem Median von 5500. An 6,6% der Orte war er 〈2000, an 26,6% 〉 10000. 6 Arten wurden an 〉 50% der Orte gefunden und machten 27,7% des gesamten Samenvorrats aus: Anagallis arvensis L., Chenopodium album L., Stellaria media (L.) Vill., Echinochloa crusgalli (L.) P. Beauv., Amaranthus spp., Polygonum persicaria L. +Polygonum lapathifolium L. Insgesamt wurden 63 Arten gefunden, an den einzelnen Orten zwischen 4 und 25, im Mittel 11. Zur Lebensform der Therophyten zählten 90,6% der Arten und 94,3% der Samen. 24,9% waren indifferente, 21,9% Frühjahrs-, 39,8% Sommer-, 5,3% Herbst-und 8,1% Winterkeimer. Der Simpson-Dominanzindex der potentiellen Flora reichte von 0,11 bis 0,525 mit einem Mittelwert von 0,21 und einem Median von 0,195. Der Shannon-Diversitätsindex lag zwischen 1,15 und 2,43 mit einem Mittelwert von 1,93 und einem Median von 1,91. In einigen Fällen (13,3%) war eine deutliche Kompensation der Arten erkennbar. Anhand der Befunde werden die Wirksamkeit und die Grenzen einer Strategie zur Verringerung des Samenvorrats im Boden diskutiert.
    Type of Medium: Electronic Resource
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  • 4
    Publication Date: 2014-06-11
    Description: Morphogenesis occurs in 3D space over time and is guided by coordinated gene expression programs. Here we use postembryonic development in Arabidopsis plants to investigate the genetic control of growth. We demonstrate that gene expression driving the production of the growth-stimulating hormone gibberellic acid and downstream growth factors is first...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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