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  • 1985-1989  (5)
  • 1950-1954  (10)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Geochemical aspects of aqueous iron, phosphorus and dissolved organic carbon in the humic Lake Tjeukemeer, The Netherlands (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 16 (1986), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The main source of P, Fe and DOC in the humic Lake Tjeukemeer is superfluous water pumped from surrounding peaty polders. Most particulate P is intracellular but almost all particulate Fe is abiotic.2. The size and molecular weight of the P, Fe and DOC (mainly fulvic acids (FA)) were determined by ultrafiltration and Sephadex G-100 gel filtration. Throughout the year most dissolved P and Fe was in colloids 〉35 nm with apparent molecular weight between 30,000 and 150.000. The bulk of FA occurred in particles 〈35nm.3. Calculating the atomic ratios of P, Fe and organic C in the different size classes revealed that Fe-FA chelates are a minor species of the Fe pool. Less than 10% of the fulvic acids occurred as Fe-FA chelates.4. Based on their apparent size and molecular weight, the Fe-FA chelates are colloidal aggregates, probably with the formula Fen-1(FA)n.5. About 50% of the dissolved P had the same size as the Fe-FA aggregates. These aggregates were only noticeable in winter when humus-rich polder water was flushed through the lake. During the rest of the year the dissolved Fe and P consisted mainly of acid-labile inorganic colloids which might have been organically coated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1986.tb01008.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Copper complexation in eutrophic and humic Lake Tjeukemeer, The Netherlands (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 21 (1989), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Copper(II) complexation in the eutrophic. humus-rich Lake Tjeukemeer was measured fortnightly for several years by copper titration (Ion Selective Electrode) and by copper solubilization. Additionally, the copper speciation during titration was followed by ultrafiltration.2. The Tjeukemeer showed high ligand concentrations able to complex up to 8.5X10-5 M Cu.3. Scatchard plots and affinity spectra of the titration data allowed the discrimination of at least three different binding sites. In Scatchard plots log K values ranged from 5 to 9, in affinity spectra from 4.5 to 8.4. The highest log K values coincided with relatively low humus concentrations and blooms of algae, mainly Cyanobacteria.5. The ultrafiltration experiments indicated that relatively small size fractions (〈10 nm) have the highest copper binding affinity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1989.tb01375.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Manipulation of chemistry and phytoplankton by hydrological intervention: a whole lake experiment in the northern Netherlands (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 20 (1988), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The small Lake Negenmad, in the nature reserve ‘De Oude Venen’, was isolated from the canals and lakes of the Frisian lake system. Its chemistry and phytoplankton were monitored 1 year before (1984) and 2 years after (1985–86) isolation. These characteristics were compared with those of the adjacent Lake Veertigmad which was not manipulated.2. The hydrological intervention prevented the inflow of chloride-rich IJsselmeer water into Lake Negenmad and made its water table more dependent on evapotranspiration, precipitation and upwelling water. In comparison with the unmanipulated lake. Lake Negenmad became less saline (c. 50%), more humic (c. 50%) and total dissolved (〈0.2,μm) iron concentration increased dramatically.3. During the 2 years of damming no marked differences in the total nutrient concentrations of either lake were observed. However, the maximum phytoplankton density in the dammed lake was half that in the unmanipulated lake. The lower density may have been caused by low P availability after formation of humus-iron phosphate species.4. Preventing the inflow of water from the Frisian lake system favoured the occurrence in Lake Negenmad of flagellated species (Chrysophyceae, Cryptophyceae) at the expense of filamentous and nuisance-causing cyanobacteria (Oscillutoria, Anabaena, Aphanizomenon spp.).5. The implications of these results for water quality management of reservoirs in peaty areas are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1988.tb00465.x
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphorus transformations in the epilimnion of humic lakes: abiotic interactions between dissolved humic materials and phosphate (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 19 (1988), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. Sephadex gel filtration of filtered water from small, Finnish forest lakes demonstrated abiotic movement of 33P from added PO4 to two higher molecular weight fractions. This movement was most pronounced in waters with high humic content which also had high iron content. The two fractions which took up 13P had nominal molecular weights of 〉 100,000 and 10,000-20,000.2. An equilibrium existed between free PO4 and the two fractions. However, one fraction, at least, appeared to exist in two phases, with one phase in rapid equilibrium with free PO4 but the other in only slow equilibrium.3. Additions of ferric iron up to 1 mg Fe l−1 to the filtered lake water stimulated movement from free PO4, provided high concentrations of humic materials were present. In the absence of humic materials even 0.1 mg Fe 1−1 would precipitate all added 33PO4.4. The high molecular weight P was only partially reactive with standard molybdate reagents. Exposure of the high molecular weight P to sunlight caused a small release of PO4 under the experimental conditions employed.5. Possible implications for biological phosphorus demand of such sequestration of free PO4 by humic materials in combination with iron are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1988.tb00357.x
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  • 5
    Electronic Resource
    Electronic Resource
    Does ionic strength affect the configuration of aquatic humic substances, as indicated by gel filtration? (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 17 (1987), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. 1. The effect of ionic strength on the configuration of aquatic humic substances was studied by gel filtration and dialysis of water from small. Finnish forest lakes of varying colour.2. Sephadex gel filtration of water from the most humic lake gave similar elution profiles of UV absorbance and dissolved organic carbon (DOC). Gel filtration of unconcentrated samples from all three lakes under natural conditions of ionic strength (I = 1.7 × 10−4) and pH (5.5–6.0) gave similar fractionation of humic substances, despite their widely differing colour (30–350 mg Pt l−1) and DOC (5–25mg C l−1).3. Increasing the ionic strength by two orders of magnitude caused considerable retardation on the Sephadex columns of the humic substances, suggesting a decrease in their molecular size and/or shape.4. Dialysis experiments strongly indicated that ionic strength-induced changes in the configuration of the aquatic humic substances are indeed real. Hence it is probable that the elution behaviour of aquatic humic substances on Sephadex gels has previously been wrongly attributed to ionic strength-dependent interactions between the gel and the humic substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01066.x
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  • 6
    Electronic Resource
    Electronic Resource
    Periklinale chimaeren bij knopmutanten (1952)
    Springer
    Euphytica 1 (1952), S. 49-56 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01902804
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  • 7
    Electronic Resource
    Electronic Resource
    Flax breeding and flax varieties in The Netherlands (1952)
    Springer
    Euphytica 1 (1952), S. 212-218 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Samenvatting Vlasveredeling in Nederland De oudste gegevens over vlasveredeling in Nederland dateren uit 1816, toen de landbouwer G.Jensma teTernaard (ten noorden vanDokkum) een aantal witbloeiende planten in Russisch blauwbloei opmerkte en deze bij de oogst afzonderde. De moderne vlasveredeling stamt uit het begin van deze eeuw. L.Broekema te Wageningen was de eerste in Nederland, die lijnselectie bij vlas toepaste (omstreeks 1900). Het gelukte de kwekers J. C.Dorst en P. J.Hijlkema belangrijke resultaten te bereiken. Ook in het buitenland hebben verschillende Nederlandse rassen verbreiding gevonden. De kwekersarbeid van de jonge kweker J. P.Wiersema is veelbelovend. Enige gegevens over de vlasveredeling in Nederland zijn neergelegd in de tabellen. Tabel 1 geeft een overzicht van de rassenstatistiek van vlas in Nederland in de jaren 1946–1951. Daaruit blijkt, dat de Nederlandse rassen geheel overheersen en van de buitenlandse momenteel alleen Liral Crown op kleine schaal wordt verbouwd. In tabel 2 zijn de kwekersvergoedingen over het oogstjaar 1949 vermeld. Tabel 3 omvat de afstamming van de rassen, die op de Nederlandse rassenlijst zijn geplaatst of daarvan zijn geschrapt. De afstamming (selectie uit landras of gekweekt ras, resp. kruising) en het aantal jaren, dat nodig was om het ras te kweken, zijn vermeld.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01910662
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  • 8
    Electronic Resource
    Electronic Resource
    Potato breeding in the Netherlands (1953)
    Springer
    Euphytica 2 (1953), S. 113-121 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00038910
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  • 9
    Electronic Resource
    Electronic Resource
    Vaktijdschriften op het gebied van de plantenveredeling (1952)
    Springer
    Euphytica 1 (1952), S. 60-61 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The English abstracting journal „Plant Breeding Abstracts” gives a satisfactory synopsis of books on plant breeding and of articles in this field that have appeared in general and professional journals. In the above survey are mentioned the following periodicals: Sveriges Utsädesföreningstidskrift (1891 →), Zeitschrift für Pflanzenzüchtung (1913 →), Der Züchter (1929 →), Agri Hortique Genetica (1943 →), Indian Journal of Genetics and Plant Breeding (1941 →), Melhoramento (1948 →), Annales de l'Amélioration (1951 →) and Euphytica, Netherlands Journal of Plant Breeding (1952 →).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01902806
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  • 10
    Electronic Resource
    Electronic Resource
    Maintaining varieties of self-fertilized crop plants (1953)
    Springer
    Euphytica 2 (1953), S. 37-45 
    Details
    ISSN: 1573-5060
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Samenvatting In de handboeken over plantenveredeling vindt men weinig over de instandhouding der rassen. Men zou daaruit de indruk kunnen krijgen, dat de instandhouding der rassen het noemen niet waard is of niet behoort tot de plantenveredeling. Bij de instandhouding worden kwekersmethoden toegepast, terwijl dit geschiedt op het kweekbedrijt. Instandhouding van door zaad vermeerderde gewassen is kwekersarbeid, ze is het verlengstuk van het scheppen van een ras. Wanneer een ras aan zichzelf wordt overgelaten, treedt ontaarding op. Hiervoor zijn verschillende oorzaken te noemen. Eensdeels kunnen deze liggen op genetisch gebied (bastaardnatuur van jonge rassen, spontane kruisbestuiving met andere rassen, mutatie, optreden van nieuwe physio's van schimmels, etc.), anderdeels zijn het mechanische oorzaken (vermenging met andere rassen of andere gewassen, etc.). In de strijd tegen de ontaarding der rassen dienen verschillende methoden toegepast te worden, o.a. het voorkómen van vermenging, voorzorgsmaatregelen in verband met ziektebestrijding, vermijding van naamsverwisseling, opzuiveren, instandhouding van het ras. Aan de hand van enige voorbeelden wordt het opbouwen van het ras toegelicht. Door stamselectie worden typische lijnen verkregen; vermeerdering van één lijn of een lijnenmengsel levert het kwekerszaad (breeder seed); eenmalige vermeerdering hiervan levert het elitezaad (foundation seed) en dit het originele zaad (registered seed), dat in het verkeer komt. Verschillende problemen bij de instandhouding van zelfbevruchters passeerden de revue, o.a. instandhouding van jonge rassen, verbetering van het ras tijdens de instandhouding, het uitgangsmateriaal voor de instandhouding, isolatie der lijnen, instandhouding der lijnen, enz. De instandhouding van landrassen dient te geschieden in het oorspronkelijke gebied zonder speciale selectie en bij voorkeur onder dezelfde omstandigheden van cultuur als vanouds gebruikelijk waren. Bij het instandhouden van geniteurs wordt dikwijls massaselectie toegepast door afwijkende planten te verwijderen of door een aantal typische planten te oogsten.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035740
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