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  • 1
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    Entomologia experimentalis et applicata 92 (1999), S. 205-216 
    ISSN: 1570-7458
    Keywords: Samea multiplicalis ; Spodoptera pectinicornis ; Pistia stratiotes ; waterlettuce ; nitrogen utilization efficiency ; compensatory feeding ; nitrogen ; biological control of weeds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Compensatory responses of caterpillars fed low quality food include increased consumption and utilization of essential nutrients. Information about an insect's responses to nutritional challenges from their host plants could benefit weed biological control efforts in the selection and establishment of new agents. The target weed, Pistia stratiotes L. (Araceae) is a floating aquatic plant that has relatively low nitrogen levels which are further diluted with high water content. Efforts to establish the insect Spodoptera pectinicornis (Hampson) (Lepidoptera: Noctuidae) for biological control of P. stratiotes could benefit by examining the nutritional responses of a similar widely established lepidopteran species, Samea multiplicalis (Guenèe) (Lepidoptera: Pyralidae). Larvae of this species were fed leaves of P. stratiotes plants that had been fertilized (NPK) at high and low rates. The leaves of the fertilized plants had a 4.3-fold increase in nitrogen (dry weight) and a 1.6-fold increase in water content. The results suggest that no compensatory increases occurred in larvae fed leaves from the low fertilized plants as no changes were found in fresh mass consumption or nitrogen utilization efficiency. Consequently, development time from second-third instars to pupation was delayed about 3 days compared with larvae fed the high nitrogen leaves. Furthermore, consumption of nitrogen was only 30% and its accumulation into larval tissues was only 60% compared with the larvae fed the high fertilized leaves. The resulting larvae had both a final biomass and a growth rate that were reduced by 40%. Regardless of plant fertilizer level, the larvae fed at a rate 5–10 times greater than that of similar lepidopteran species consuming either low or high quality diets, suggesting that the S. multiplicalis larvae may be functioning at their biological limit for ingesting food.
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  • 2
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    Entomologia experimentalis et applicata 92 (1999), S. 165-177 
    ISSN: 1570-7458
    Keywords: Chrysomelidae ; herbivory ; Asteraceae ; life history ; nitrogen ; plant quality ; season
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phytophagous insects which feed on the leaves of herbaceous host plants have to adapt their life histories to the fact that protein nitrogen is usually highest in growing tissues in spring. We monitored field populations of larvae and adults of three chrysomelid species (Galeruca tanaceti (L.) (main host Achillea millefolium (L.) Yarrow), Cassida rubiginosa (Mueller) (main host Cirsium arvense (L.) Scop.) and Oreina luctuosa (Suffrian) (host Centaurea scabiosa (L.)) together with the amount of protein nitrogen of their food resources and host plant biomass. As expected, the development of host quality, measured as concentration of protein nitrogen, and host plant biomass showed inverse trends during the season. The euryphagous G. tanaceti attacks Achillea early and profits from high nitrogen concentrations in the leaves. Occasional overexploitations of local populations of Achillea are compensated by the capacity to move to other host species. In C. rubiginosa, a species with a host range restricted to the Cardueae, the main larval feeding activity is postponed to a period when the nitrogen content of the host leaves had dropped to 50% of its initial value, but when host plant biomass had increased by 30%. In the monophagous O. luctuosa the larval development is synchronized with a still later phase of host phenology, at which the nitrogen content is below 50% but plant biomass has reached its maximum. There seem to be selection factors, which oppose the use of high quality food in spring and which force the latter two species to postpone their larval development to a later time in the year. This could be caused by numerous factors like, for example, mean daytime temperature. Later in the season the larvae have to cope with the low quality of their host plants. They have, however, the advantage of large quantities of food available. A laboratory study with adults and mature larvae of O. luctuosa shows that this species can overcome low levels of protein nitrogen either by selecting younger leaves with higher nitrogen concentrations or by increasing the daily food consumption rate (RCR) on leaves with a low level of nitrogen and by a prolongation of the feeding period. In this way the larvae compensate the effect of lower daily growth rates (RGR) and a lower food conversion index (ECI) on poor food quality: Regardless of the level of protein nitrogen there was no statistically significant difference in total gain of weight during the third-instar feeding period and in the weight at the end of the third larval stage. The three investigated chrysomelids show that there exists a broad spectrum of adaptations to overcome the dilemma of variable food quality.
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  • 3
    ISSN: 1572-879X
    Keywords: adsorption ; adsorption isotherms ; dinitrogen ; FTIR spectroscopy ; geminal species ; NaY ; nitrogen ; zeolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of N2 on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm−1 (2255.4 cm−1 after adsorption of 15N2). With decreasing equilibrium pressure the complexes tend to loose one N2 ligand, thus forming linear species characterized by an IR band at 2336.8 cm−1 (2258.7 cm−1 after adsorption of 15N2). All species disappear completely after evacuation. Co-adsorption of N2 and CO revealed that the dinitrogen complexes are formed on Na+ cations. The changes in the concentrations of the linear and geminal N2 species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls.
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  • 4
    ISSN: 1572-8757
    Keywords: kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
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  • 5
    ISSN: 1432-1890
    Keywords: Key words PCR ; RFLP ; ITS sequence analysis ; Ectomycorrhizal fungi ; Cortinarius taxonomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The ability of restriction fragment length polymorphism (RFLP) analysis of the rDNA internal transcribed spacer (ITS) region to discriminate 10 co-occurring Cortinarius and Dermocybe species at a southeastern Australian sclerophyll forest site was assessed. Using the basidiomycete-specific primers ITS1F and ITS4B, some taxa were separated on the basis of individual RFLP patterns derived using the restriction endonucleases Hae III or Hinf I. Combined data from both endonucleases were, however, required to separate all taxa [Dermocybe austro-veneta Clel. (Moser & Horak), C. rotundisporus Clel. & Cheel, C. archeri Berk., C. sinapicolor Clel., C. violaceus (L.: Fr.) S.F.Gray, C. radicatus Clel. and four morphologically-distinct, but unidentified Cortinarius spp.]. ITS sequence comparisons confirmed that D. austro-veneta belongs in Dermocybe, that C. rotundisporus is correctly placed in subgenus Phlegmacium, and suggest that Australian C. violaceus collections are not conspecific with northern hemisphere C. violaceus.
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  • 6
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    Nutrient cycling in agroecosystems 53 (1999), S. 209-218 
    ISSN: 1573-0867
    Keywords: cattle slurry ; fertilizer splitting ; nitrogen ; recovery ; residual nitrogen ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The recovery of soil mineral nitrogen (N) by crops, and its subsequent utilisation for dry matter (DM) production may be increased when the application of N is postponed until after crop emergence. The significance of this strategy for silage maize was studied in nine field experiments on Dutch sandy soils from 1983 to 1988. In five experiments the effect of slurry applied before planting at a rate of circa 66 m3 ha-1, was compared to the effect of a similar rate of which half was applied before planting and half at the 4–6 leaf stage. In the 4-6 leaf stage slurry was either injected or banded. In four other experiments the effect of mineral fertilizer-N splitting was studied. In these experiments, 30 m3 ha-1 cattle slurry, applied before planting, was supplemented with mineral fertilizer-N at rates ranging from 40 to 160 kg ha-1, either fully applied before crop emergence or split. When split, 40 kg ha-1 of the mineral fertilizer-N rate was banded at the 4–6 leaf stage. According to balance sheet calculations, substantial losses of slurry N and mineral fertilizer-N occurred during the growing season. Losses were compensated for, however, by apparent mineralization, ranging from 0.34 to 0.77 kg N ha-1 day-1. Split applications of cattle slurry had a significant positive effect on the DM yield in two out of five experiments compared to the conventional non-split application, but only when the post-emergence slurry application was banded which is no longer in accordance with present legislation. Split applications of mineral fertilizer-N had a significant positive effect in one experiment where rainfall was excessive but not in the others. The results provide insufficient evidence to recommend farmers to split applications. Soil mineral N sampling at the 4–6 leaf stage should hence be considered a control on the appropriateness of early N applications after exceptional weather conditions rather than a routine observation on which the post-emergence N dressing is to be based in a deliberate splitting strategy. Our data suggest that the financial return of a 40 kg ha-1 supplementation with mineral fertilizer-N, was questionable when more than 175 kg N ha-1 were found in the upper 0.6 m soil layer at the 4–6 leaf stage.
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  • 7
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    Nutrient cycling in agroecosystems 53 (1999), S. 259-267 
    ISSN: 1573-0867
    Keywords: farming systems ; nitrogen ; nitrogen budgets ; sustainability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three approaches to nitrogen budgeting were developed and their ability to quantitatively describe nitrogen cycling in a fertilizer based and a grass–clover based beef system tested. Budgets ranged in complexity from the Economic Input:Output (EIO) budget, which accounted simply for purchases and sales of nitrogen over the farmgate, through the Biological Input:Output (BIO) budget, which included estimates of biological nitrogen fixation and attempted to partition losses into leaching and gaseous forms, to the Transfer:Recycle:Input:Output (TRIO) budget, which also accounted for key soil processes. Nitrogen unaccounted for in the fertilized system decreased with increasing budget complexity (285, 212 and 188 kg ha-1 yr-1 unaccounted for by the EIO, BIO and TRIO budgets, respectively). In the legume based grass–clover system, the EIO budget did not accurately describe total nitrogen inputs as it did not include 146 kg ha-1 yr-1 from symbiotic nitrogen fixation. In the grass–clover system, nitrogen unaccounted for was again greater using the BIO than the TRIO budget (103 and 79 kg ha-1 yr-1, respectively). In conclusion, the most complex budgeting approach (TRIO) was able to account for the fate of a greater proportion of nitrogen inputs than the simpler approaches. However, the perceived success of the different approaches was strongly dependent on the precise objective.
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  • 8
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    Nutrient cycling in agroecosystems 55 (1999), S. 1-6 
    ISSN: 1573-0867
    Keywords: chlorophyll meter ; irrigation ; LAI ; nitrogen ; Spring Wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A Spring Wheat crop was grown using three irrigation levels and nitrogen rate applications to evaluate chlorophyll meter measurements as a possible nitrogen nutrition index for modelling. These measurements yielded the most reliable indications at Zadoks GS45. The lower limit indicating severe nitrogen deficiency in the leaves was approximately 35 SPAD units while the upper limit of 45 SPAD units, indicated an excess consumption.
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  • 9
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    Nutrient cycling in agroecosystems 55 (1999), S. 89-94 
    ISSN: 1573-0867
    Keywords: algae ; flooded soils ; N cycling ; nitrogen ; 15N ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Algal N labelled with 15N added to a flooded soil in laboratory columns without plants was studied to determine the changes over time in the fate of N assimilated by algae and to study how its fate is affected by (a) exclusion of light simulating complete closure of the rice canopy, and (b) addition of fertilizer-NH4 *. In the light but with no added fertilizer-N there was little net mineralization of the added algal N during the first 4 weeks, but after 8 weeks 42% had been mineralized, of which 95% was denitrified. Exclusion of light caused net mineralization to proceed more rapidly in the first 4 weeks due to the death of algal cells and lowered reassimilation. After 8 weeks 51% had been mineralized, of which 54% was denitrified, 16% volatilized and 30% was present as KCl exchangeable NH4 +-N. Application of fertilizer-NH4 + apparently caused mineralization of 25% of the algal N within one week but the results were probably affected by pool substitution in which labelled N mineralized to NH4 +-N was diluted with fertilizer – NH+ 4 and then immobilized leaving more labelled NH4–N in the mineral pool. After 8 weeks, 42% of algal N had been mineralized, of which 69% was estimated to have been denitrified, 19% lost through NH3 volatilization and 12% remained as extracted NH4 ++NO- 3. Uptake of N by a rice crop would reduce the gaseous losses. Algal N was mineralized quickly enough to be available during the growing season of a rice crop and, depending on field conditions, algae may have a role in assimilating N and protecting it from loss as well as being a major driving force for NH3 volatilization through diurnal increases in pH.
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  • 10
    ISSN: 1572-9702
    Keywords: tomato plants ; susceptibility ; mite ; tridecan-2-one ; nitrogen ; potasium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objective of this work was to study the effect of NK fertilization levels and canopy height on the resistance of Lycopersicon hirsutum and Lycopersicon esculentum to Aculops lycopersici (Acari: Eriophydae). The effects of NK fertilization levels and canopy height in the leaf size and density of trichomes and their effects on tridecan-2-one (2-TD) and undecan-2-one (2-UD) limiting the attack of A. lycopersici on tomato plants were assessed. Different NK fertilization levels had no effect on the resistance of L. hirsutum to A. lycopersici. No significant differences were found in attack rates of this mite on leaves of the top and median parts of L. hirsutum canopy. The type and density of trichomes were the main determining factor of A. lycopersici attack on tomato plants. High trichome densities and type VI glandular trichomes which produce tridecan-2-one are important resistance factors on tomato plants. L. hirsutum showed a high resistance level to A. lycopersici due to high densities of type VI glandular trichomes and consequently higher levels of tridecan-2-one in its leaves.
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  • 11
    ISSN: 1432-1211
    Keywords: Key words Interleukin (IL)-4 ; Promoter ; Polymorphism ; RFLP ; Linkage disequilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 12
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    Journal of materials synthesis and processing 7 (1999), S. 311-319 
    ISSN: 1573-4870
    Keywords: Iron ; carbon ; nitrogen ; microstructure ; characterization ; HIP-drip
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A new processing technique makes nitrogen alloying possible by adding nitrogen under elevated nitrogen pressure to prealloyed Fe-C ingots during continuous casting, producing a whole new class of precipitation-free, iron–carbon–nitrogen alloys. When both carbon and nitrogen bulk concentration levels exceeded 0.5 wt%, a duplex fcc-/(bcc-bct-) Fe microstructure resulted that is iron carbide- and nitride-free. With increasing carbon and nitrogen concentrations, there was an increase in the retained fcc-Fe phase. In cooling rate studies, increasing carbon and nitrogen concentrations shifted the knee of the fcc-Fe-to-bcc-Fe phase time–temperature–transformation (T–T–T) curve to longer times. Hardness, compression strength, and wear resistance increased with increasing carbon and nitrogen concentrations and were superior to iron–carbon alloys without the nitrogen addition.
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  • 13
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    Theoretical and applied genetics 98 (1999), S. 291-298 
    ISSN: 1432-2242
    Keywords: Key words DNA ; Molecular evolution ; Parsimony ; PAUP ; Phylogeny ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Chloroplast DNA of 22 species of Acacia (Tourn.) Miller was digested with ten restriction endonucleases, Southern-blotted and probed with cloned fragments covering the chloroplast genome of tobacco (Nicotiana tabacum L.). Phyletic and phenetic analyses of the resulting 176 polymorphic bands recorded among the 22 species were performed. The phylogram was reconstructed using heuristic search and Wagner parsimony. The resulting most parsimonious consensus phylogram displayed three major phyletic lineages, consistent with the previously established three subgenera of Acacia. The 10 species of subgenus Acacia and the 6 species of subgenus Heterophyllum formed two monophyletic sister clades. The 5 species of subgenus Aculeiferum studied and Acacia albida (Syn. Faidherbia albida) grouped together and were basal to the clades of subgenera Acacia and Heterophyllum. The phylogram indicated that subgenus Heterophyllum diverged earlier from subgenus Aculeiferum than did subgenus Acacia; however, the phenogram indicated the reverse. The study indicated that A. nilotica and A. farnesiana are sister species, though A. nilotica is Afro-Asiatic and A. farnesiana is American. The phenogram separated the three subgenera in agreement with the phylogram, but the two dendrograms differed regarding the topologies of the species and the distance of evolution between subgenera Acacia and Heterophyllum.
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  • 14
    ISSN: 1432-2242
    Keywords: Key words Linkage analysis ; Mapping populations ; Introgression Lines ; RFLP ; Host range
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The soil-borne fungi Verticillium spp. cause vascular wilt disease in a wide range of crop plants. In tomato, resistance to Verticillium dahliae race 1 is conferred by a single dominant gene, Ve. Previous efforts to map Ve in tomato have yielded confusing results, locating it on different chromosomes, which subsequently raised the possibility that Verticillium resistance may be controlled by a number of loci. We used three different mapping populations to obtain an unambiguous map location of Ve: a recombinant inbred (RI) line population; an F2 population segregating for Verticillium resistance; and a population of 50 introgression lines (IL). In all of the mapping populations Ve was positioned on the short arm of chromosome 9 tightly linked to the RFLP marker GP39. This linkage was confirmed by screening for GP39 in different breeding lines with known resistance or susceptibility to Verticillium. A perfect match was found between GP39 and the Verticillium response of the lines, indicating the potential of GP39 in the rapid detection of Verticillium resistance and as a starting point for map-based cloning of Ve. This approach is particularly relevant for Verticillium dahliae race 1, since in the present work we also show that the isolate that infects tomato is responsible for wilt disease in other important crop plants.
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  • 15
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    Theoretical and applied genetics 98 (1999), S. 1163-1170 
    ISSN: 1432-2242
    Keywords: Key wordsTriticum aestivum ; Triticum spelta ; RFLP ; Genetic map ; QTL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We constructed a genetic map of a cross between the Swiss winter wheat (Triticum aestivum L.) variety Forno and the Swiss winter spelt (Triticum spelta L.) variety Oberkulmer. For the linkage analysis,176 polymorphic RFLP probes and nine microsatellites were tested on 204 F5 recombinant inbred lines (RILs) of Forno×Oberkulmer revealing 242 segregating marker loci. Thirty five percent of these loci showed significant (P〉0.05) deviation from a 1 : 1 segregation, and the percentage of Forno alleles ranged from 21% to 83% for individual marker loci. Linkage analysis was performed with the program MAPMAKER using the Haldane mapping function. Using a LOD threshold of 10, we obtained 37 linkage groups. After finding the best order of marker loci within linkage groups by multi-point analysis we assembled the linkage groups into 23 larger units by lowering the LOD threshold. All except one of the 23 new linkage groups could be assigned to physical chromosomes or chromosome arms according to hybridisation patterns of nulli-tetrasomic lines of Chinese Spring and published wheat maps. This resulted in a genetic map comprising 230 marker loci and spanning 2469 cM. Since the analysed population is segregating for a wide range of agronomically important traits, this genetic map is an ideal basis for the identification of quantitative trait loci (QTLs) for these traits.
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  • 16
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    Theoretical and applied genetics 99 (1999), S. 593-598 
    ISSN: 1432-2242
    Keywords: Keywords Maize ; Head smut ; Sporisorium reiliana ; QTL ; RFLP ; Ustilago maydis ; Puccinia sorghi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We mapped and characterized quantitative trait loci (QTL) for resistance to Sporisorium reiliana. A population of 220 F3 families produced from the cross of two European elite inbreds (D32, D145) was evaluated with two replications at a French location with high natural incidence of S. reiliana and at a Chinese location employing artificial inoculation. The 220 F3 families were genotyped with 87 RFLP and seven SSR markers. Using composite interval mapping, we identified two different sets of 3 and 8 QTL for the French and the Chinese locations explaining 13% and 44% of respectively. Individual QTL explained up to 14% of σ^2 p. The 11 QTL mapped to eight maize chromosomes and displayed mostly additive or partial dominant gene action. Significant digenic epistatic interactions were detected for one pair of these QTL. Only a few QTL for S. reiliana were in common with QTL for resistance to Ustilago maydis and Puccinia sorghi, identified at a German location for the same population. Consequently, in our materials resistance to these three fungal pathogens of maize seems to be inherited independently.
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  • 17
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    Theoretical and applied genetics 99 (1999), S. 727-732 
    ISSN: 1432-2242
    Keywords: Key words Hordeum vulgare ; BaYMV ; Resistance gene ; RFLP ; Mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The rym3 (formerly designated ym3) gene conferring resistance to barley yellow mosaic virus (BaYMV) is effective against all strains of the virus but up to now has not been mapped to any chromosome. We performed a linkage analysis, using DNA extracted from individually harvested mature leaves of 153 F2 plants derived from a cross between BaYMV-resistant cv ’Ishuku Shirazu’ carrying rym3 and susceptible cv ’Ko A’. Additionally, the F3 lines derived from F2 plants were grown in the BaYMV-infested field and examined for their reaction to BaYMV. Our results indicated that rym3 is located on the short arm of chromosome 5H and flanked by RFLP markers MWG28and ABG705A at distances of 7.2 and 11.7 cM, respectively. The chromosomal configuration estimated by DNA markers around rym3 and the utilization of these molecular markers for pyramiding with the BaYMV resistance genes in barley breeding programs are discussed.
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  • 18
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    Theoretical and applied genetics 99 (1999), S. 58-64 
    ISSN: 1432-2242
    Keywords: Key words Genetic map ; RFLP ; AFLP ; RAPD ; SAMPL ; Daucus carota L. ssp. sativus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A 109-point linkage map consisting of three phenotypic loci (P 1, Y 2, and Rs), six restriction fragment length polymorphisms (RFLPs), two random amplified polymorphic DNAs (RAPDs), 96 amplified fragment length polymorphisms (AFLPs), and two selective amplification of microsatellite polymorphic loci (SAMPL) was constructed for carrot (Daucus carota L. ssp. sativus; 2n=2x=18). The incidence of polymorphism was 36% for RFLP probes, 20% for RAPD primers, and 42% for AFLP primers. The overall incidence of disturbed segregation was 18%. Linkage relationships at a LOD score of 4.0 and θ=0.25 indicated 11 linkage groups. The total map length was 534.4 cM and the map was clearly unsaturated with markers spaced at 4.9 cM. AFLP P6B15 was 1.7 cM from P 1, AFLP P1B34 was 2.2 cM from Y 2, and AFLP P3B30XA was 8.1 cM from Rs.
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  • 19
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    Theoretical and applied genetics 99 (1999), S. 1053-1060 
    ISSN: 1432-2242
    Keywords: Key words Sugarcane cultivars ; Linkage disequilibrium ; Foundation bottleneck ; Interspecific hybrids ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Modern sugarcane cultivars are derived from a few interspecific hybrids created early in this century. Linkage disequilibrium was investigated in a population of 59 cultivars representing the most important commercial clones bred in Mauritius as well as a few old cultivars involved in their genealogy. Thirty-eight probes scattered over the sugarcane genome map were used to reveal RFLPs. Forty-two cases of bilocus associations were observed involving a total of 33 loci. Most of them are separated by less than 10 cM. All the corresponding allele couples were found in at least 1 of the originally created cultivars, suggesting that they depict ancient associations. This global disequilibrium is interpreted as the result of the foundation bottleneck related to the first interspecific crosses; the preferential allele associations thus created have been maintained through subsequent crosses when the loci were closely linked. This phenomenon is likely also to apply to genes of agricultural interest. A practical consequence is that markers can be used to track known QTLs in modern breeding materials without the necessity to repeatedly study segregating progenies. This structure gives high value to the correlation between molecular markers and agricultural traits among cultivars.
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  • 20
    ISSN: 1432-2242
    Keywords: Key words Brassica oleracea ; S haplotype ; Self-incompatibility ; RFLP ; IEF
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Forty three S tester lines of Brassica oleracea were characterized using DNA and protein gel-blotting analyses. DNA gel-blot analysis of HindIII-digested genomic DNA with class-I and class-II SLG probes revealed that 40 lines could be classified as class-I S haplotypes while three lines could be classified as class-II S haplotypes. The band patterns in the S tester lines were highly polymorphic. Although the S tester lines typically showed two bands corresponding to SLG and SRK in the analysis with the class-I SLG probe, only one band was observed in the S 24 homozygote. This band was identified as SRK, suggesting that this haplotype has no class-I SLG band. In the analysis using the class-II SLG probe, one plant yielded a different band pattern from the known class-II haplotypes, S 2 , S 5 and S 15 . Unexpectedly, this plant was reciprocally cross-incompatible with the S 2 haplotype. Therefore, it was designated as S 2-b . We found an S 13 haplotype having a restriction fragment length polymorphism different from that of the S 13 homozygotes of the S tester line. These findings indicate that S homozygous lines with the same S specificity do not necessarily show the same band pattern in the DNA gel-blot analysis. Soluble stigma proteins of 32 S homozygotes were separated by isoelectric focusing and detected using anti-S 22 SLG antiserum. S haplotype-specific bands were detected in 27 S homozygotes but not in five S homozygotes, including the S 24 homozygote. This is consistent with the observation that the S 24 haplotype had no SLG band.
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  • 21
    ISSN: 1432-2242
    Keywords: Key words Cotton ; Gossypol ; Wide hybridization ; Backcrossing ; DNA markers ; AFLP ; RFLP ; Introgression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  This work aims at breeding upland cotton [Gossypium hirsutum L., 2(AD)1 genome] with a reduced level of gossypol in the seeds for optimal food and feed uses, and a high gossypol level in the remaining organs for resistance to pests. Two tri-species Gossypium hybrids, (G. thurberi–G. sturtianum–G. hirsutum and G. hirsutum–G. raimondii–G. sturtianum) including G. sturtianum (2C1) as a donor, G. thurberi (2D1) and G. raimondii (2D5) as a bridge species, were created. Recurrent selection initiated with these tri-species hybrids produced backcross (BC) progenies expressing the ”low-gossypol seed and high-gossypol plant” trait at different levels. We used AFLP markers to assess the genetic similarity among the germplasm and RFLP probes to tag the introgression of specific chomosome segments from the parental species. Five pairs of AFLP primers generated 477 fragments, among which 417 (87.4%) were polymorphic. The genetic similarity between the upland cotton and the wild species ranged from 29.5 to 43.2%, while similarity reached 80% between upland cotton and BC3 plants. Introgression of species-specific AFLPs was evident from all the parental species and confirmed the hybrid origin of the analyzed progenies. Southern-blot analysis based on 49 RFLP probes allowed us to trace the introgression of parental DNA segments in the tri-species hybrids and in three generations of backcross. Introgression was evident from 11, 8 and 7 linkage groups of G. sturtianum, G. raimondii and G. thurberi respectively. The types of introgression revealed by RFLP probes are discussed, and breeding schemes to enhance recombination are proposed. The ability to trace DNA segments of known chromosomal locations from the donor G. sturtianum through segregating generations is a starting point to map the ”low-gossypol seed and high-gossypol plant” traits.
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  • 22
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    Theoretical and applied genetics 98 (1999), S. 356-364 
    ISSN: 1432-2242
    Keywords: Key words SCN ; RFLP ; QTL ; Molecular marker ; Soybean
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, causes severe damage to soybean [Glycine max (L.) Merr] throughout North America and worldwide. Molecular markers associated with loci conferring SCN resistance would be useful in breeding programs using marker-assisted selection (MAS). In this study, 200 F2:3 families derived from two contrasting parents, SCN-resistant ‘Peking’ with relatively low protein and oil concentrations, and SCN-susceptible ‘Essex’ with high protein and oil concentrations, were used to determine loci underlying the SCN resistance and seed composition. Three different SCN Race isolates (1, 3, and 5) were used to screen both parents and F2:3 families. The parents were surveyed with 216 restriction fragment length polymorphism (RFLP) probes with five different restriction enzymes. Fifty-six were polymorphic and contrasted with trait data from bioassays to identify molecular markers associated with loci controlling resistance to SCN and seed composition. Five RFLP markers, A593 and T005 on linkage group (LG) B, A018 on LG E, and K014 and B072 on LG H, were significantly linked to resistance loci for Race 1 isolate, which jointly explained 57.7% of the total phenotypic variation. Three markers (B072 and K014, both on LG H; T005 on LG B) were associated with resistance to the Race 3 isolate and jointly explained 21.4% of the total phenotypic variation. Two markers (K011 on LG I, A963 on LG E) associated with resistance to the Race 5 isolate together explained 14.0% of the total phenotypic variation. In the same population we also identified two RFLP markers (B072 on LG H, B148 on LG F) associated with loci conferring protein concentration, which jointly explained 32.3% of the total phenotypic variation. Marker B072 was also linked to loci controlling the concentration of seed oil, which explained 21% of the total phenotypic variation. Clustering among quantitative trait loci (QTLs) conditioning resistance to different SCN Race isolates and seed protein and oil concentrations may exist in this population. We believe that markers located near these QTLs could be used to select for new SCN resistance and higher levels of seed protein and oil concentrations in breeding improved soybean cultivars.
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  • 23
    ISSN: 1432-2242
    Keywords: Key words Wheat microsatellites ; Linkage map ; RFLP ; T. turgidum ssp. durum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Seventy nine microsatellite markers from hexaploid bread wheat (T. aestivum L.) were integrated into a genetic linkage map of durum wheat (T. turgidum ssp. durum (Desf.) Huns.) created by RFLP segregation data from a population of 65 recombinant inbred lines. The results indicate a relatively even distribution of microsatellite loci and demonstrate that microsatellite markers from hexaploid wheat provide an excellent source of molecular markers for use in the genetics and breeding of durum wheat.
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  • 24
    ISSN: 1432-2242
    Keywords: Key words Molecular markers ; Integrated linkage map ; Tomato ; Lycopersicon species ; AFLP ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Two independent F2 populations of Lycopersicon esculentum×L. pennellii which have previously been investigated in RFLP mapping studies were used for construction of a highly saturated integrated AFLP map. This map spanned 1482 cM and contained 67 RFLP markers, 1078 AFLP markers obtained with 22 EcoRI+MseI primer combinations and 97 AFLP markers obtained with five PstI+MseI primer combinations, 231 AFLP markers being common to both populations. The EcoRI+MseI AFLP markers were not evenly distributed over the chromosomes. Around the centromeric region, 848 EcoRI+ MseI AFLP markers were clustered and covered a genetic distance of 199 cM, corresponding to one EcoRI+ MseI AFLP marker per 0.23 cM; on the distal parts 1283 cM were covered by 230 EcoRI+MseI AFLP markers, corresponding to one marker per 5.6 cM. The PstI/MseI AFLP markers showed a more even distribution with 16 PstI/MseI AFLP markers covering a genetic distance of 199 cM around the centromeric regions and 81 PstI/MseI AFLP markers covering a genetic distance of 1283 cM on the more distal parts, corresponding to one marker per 12 and 16 cM respectively. In both populations a large number of loci showed a significant skewed segregation, but only chromosome 10 loci showed skewness that was similar for both populations. This ultra-dense molecular-marker map provides good perspectives for genetic and breeding purposes and map-based cloning.
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  • 25
    ISSN: 1432-2242
    Keywords: Key words Saccharum officinarum ; Sugarcane cultivars ; Polyploid ; Genetic diversity ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Molecular diversity was analysed among 162 clones of sugarcane using DNA restriction fragment length polymorphism (RFLP). One hundred and nine of them were modern cultivars of interspecific origin; most of them were bred in Barbados or in Mauritius. Fifty three were from Saccharum officinarum species, which is the major source of genes in modern cultivars, prevailing over the part of the genome incorporated from the wild species Saccharum spontaneum. Twelve low-copy nuclear DNA probes scattered over the genome were used in combination with one or two restriction enzymes. A total of 399 fragments was identified, 386 of which were polymorphic. Each sugarcane clone displayed a high number of fragments per probe/enzyme combination, illustrating the polyploid constitution of the genome. Among the S. officinarum clones, those from New Guinea had the largest variability and encompassed that present among clones collected from the Indonesian Islands and those known to have been involved in the parentage of modern cultivars. This is in agreement with the hypothesis that New Guinea is the centre of origin of this species. The clones from New Caledonia formed a separate group and could correspond to S. officinarum clones modified through introgression with other members of the ‘Saccharum complex’. Despite the low number of S. officinarum clones used for breeding cultivars, more than 80% of the markers present in the whole S. officinarum sample were also found in modern cultivars due probably to a high heterozygosity related to polyploidy. Among the cultivars, the two main groups, originating from Barbados and Mauritius, were clearly separated. This appeared essentially due to S. spontaneum alleles present in Mauritian cultivars and absent in Barbadan ones, probably in relation to the regular use of early generation interspecific hybrids in the breeding program employed in Mauritius.
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  • 26
    ISSN: 1432-2242
    Keywords: Key words Sunflower ; Linkage mapping ; cDNA ; RFLP ; Phenotypic traits ; Composite mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A map of the sunflower genome, based on expressed sequences and consisting of 273 loci, was constructed. The map incorporates data from seven F2 populations, for a total of 1115 individuals. Two hundred and fourty five loci corresponding to 170 anonymous cDNA markers and four loci for morphological markers were mapped. We also mapped 18 loci corresponding to previously described genes or to sequences obtained through homology cloning. The unit maps vary from 774 cM to 1060 cM, with an average value of 14 major linkage groups. The integrated map is arranged in 17 major linkage groups including 238 loci, plus four small segments with 2–5 marker loci; and covers 1573 cM with an overall average marker interval of 7 cM. Thirty five percent of the markers were dominant in nature and 30% showed inter-linkage group duplication without any indication of homoeologous linkage groups. Evidence is provided for the independence of two distinct fertility restoration genes, for the presence of two loosely linked branching loci, and for marker tightly linked to the Rf1 restoration locus. This map provides an efficient tool in breeding applications such as disease-resistance mapping, QTL analyses and marker-assisted selection.
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  • 27
    ISSN: 1432-2242
    Keywords: Key words Hordeum vulgare ; Disease resistance ; Genetic mapping ; RFLP ; QTL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Spot form of net blotch (SFNB) (Pyrenophora teres f maculata) is an economically damaging foliar disease of barley in many of the world’s cereal growing areas. The development of SFNB-resistant cultivars may be accelerated through the use of molecular markers. A screen for SFNB resistance in 96 lines identified four new sources of resistance, including a feed variety, ‘Galleon’, for which a fully mapped doubled haploid population was available. Segregation data indicated SFNB resistance was conferred by a single gene in the ‘Galleon’בHaruna Nijo’ cross, positioned on the long arm of chromosome 7H. This gene is designated Rpt4 and is flanked by the RFLP loci Xpsr117(D) and Xcdo673 at distances of 6.9 cM and 25.9 cM, respectively. The marker Xpsr117(D) was validated using another population segregating for Rpt4, correctly predicting SFNB resistance with more than 90% accuracy.
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  • 28
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    Theoretical and applied genetics 99 (1999), S. 656-662 
    ISSN: 1432-2242
    Keywords: Key words Comparative mapping ; RFLP ; Microsatellite markers ; Loblolly pine ; Radiata pine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic linkage maps were constructed for loblolly pine (Pinus taeda L.) and radiata pine (P. radiata D. Don) using a common set of RFLP and microsatellite markers. The map for loblolly pine combined data from two full-sib families and consisted of 20 linkage groups covering 1281 cM. The map for radiata pine had 14 linkage groups and covered 1223 cM. All of the RFLP probes readily hybridise between loblolly and radiata pine often producing similar hybridisation patterns. There were in total 60 homologous RFLP loci mapped in both species which could be used for comparative purposes. A set of 20 microsatellite markers derived from radiata pine were also assayed; however, only 9 amplified and revealed polymorphic loci in both species. Single-locus RFLP and microsatellite markers were used to match up linkage groups and compare order between species. Twelve syntenic groups were obtained each consisting of from 3 to 9 homologous loci. The order of homologous loci was colinear in most cases, suggesting no major chromosomal rearrangements in the evolution of these species. Comparative mapping between loblolly and radiata pine should facilitate genetic research in both species and provide a framework for mapping in other pine species.
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  • 29
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    Theoretical and applied genetics 99 (1999), S. 670-675 
    ISSN: 1432-2242
    Keywords: Key words Dwarfing genes ; GA insensitivity ; Genetic mapping ; RFLP ; Hordeum vulgare
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   The two recessive dwarfing mutants gai (GA-ins) and gal (GA-less), differing in their response to exogenously applied gibberellic acid (GA3), were mapped in the centromere region and on the long arm, respectively, of the barley chromosome 2H. The gene gai, which determines reduced plant height and GA insensitivity pleiotropically, was found to co-segregate with the two RFLP markers Xmwg2058 and Xmwg2287. Both markers are known to map close to the centromere. The GA-sensitive dwarfing gene gal was found to be linked to the three co-segregating RFLP markers Xmwg581, Xmwg882 and Xmwg2212 (proximal) and XksuG5 (distal) by 3.6 and 9.5. cM, respectively. The distance between the two mutant loci was estimated to be about 55 cM. Homoeologous relationships between the dwarfing genes within the Triticeae are discussed.
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  • 30
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    Theoretical and applied genetics 99 (1999), S. 1087-1093 
    ISSN: 1432-2242
    Keywords: Key words Amphiploid ; Triticum ; Leymus ; FISH ; RFLP ; Ribosomal genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Three different amphiploid lines originated from crosses between wheat (Triticum L.) and lymegrass (Leymus Hochst.) were analysed by fluorescence in situ hybridization (FISH) using total genomic DNA and 18S.26S ribosomal genes (rDNA). Based on the genomic probes, these lines were the same in that they all were allohexaploids (2n=6x=42) containing 30 wheat and 12 lymegrass chromosomes. The ribosomal gene mapping further identified species origin of the chromosomes, whereby the lymegrass parent was undoubtedly L. mollis and the wheat was likely to be a Triticum species having the AB genomes. This rDNA mapping was also able to reveal differences in the genome composition among these lines, and such differences were mainly in the wheat nucleolar organizing regions (Nor). The first line (M) had two Nor-B1 (1BS), the second line (G) had one Nor-B1 (1BS), two Nor-B2 (6BS) and two Nor-A1 (1AS), whereas the third line (U) had the same Nor loci as the second line but two sites each. The wheat ribosomal genes were variably expressed depending on the lines, but the lymegrass loci appeared inactive. All three lines had the same Nor loci belonging to L. mollis, two Nor-m1 and two Nor-m2. Analysis of restriction fragment length polymorphism (RFLP) of the rDNA confirmed the identity of L. mollis parent in all three lines and verified the differences in the wheat ribosomal genes among them. These amphiploids were, however, similar in their restriction profiles, therefore indicating common origin. The molecular and cytogenetic evidence here suggested that these annual, fully fertile amphiploids that originated from the same crosses 40 years ago became genetically differentiated and fixed in stable forms.
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  • 31
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    Theoretical and applied genetics 98 (1999), S. 320-328 
    ISSN: 1432-2242
    Keywords: Key words Sorghum ; RFLP ; AFLP ; Genetic linkage map
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  A near-saturated sorghum genetic linkage map was produced using RFLP, AFLP and morphological markers. First a composite, essentially RFLP-based genetic linkage map was obtained from analyses of two recombinant inbred populations. This map includes 343 loci for 11 linkage groups spanning 1352 cM. Since this map was constructed with many previously mapped heterologous probes, it offers a good basis for synteny studies. Separately, an AFLP map was obtained from the analysis of 168 bands revealed from 12 primer pair combinations. It includes 137 loci for 11 linkage groups spanning 849 cM. Taking into account the different data sets, we constructed a combined genetic linkage map including 443 loci spanning 1899 cM. Two main features are to be noted: (1) the distribution of AFLPs along the genome is not uniform; (2) an important stretching of the former core map is induced after adding the AFLPs.
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  • 32
    ISSN: 1432-2242
    Keywords: Key words Resistance gene ; RFLP ; YAC contig ; Fragmentation ; Gene cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The deduced peptide sequences of 25 gene fragments of NBS-LRR resistance (R) gene homologues from rice and barley and of characterized R genes were compared, revealing a string of six conserved motifs. Mapping of the R-gene candidates in rice showed linkage to genes conferring race-specific resistance to rice blast (Pi-k, Pi-f and Pi-1) and bacterial blight disease (Xa-1, Xa-3 and Xa-4), in barley to powdery mildew (Mla) and the rust fungus (Rpg1). In rice four mixed clusters were detected, each harboring at least two highly dissimilar NBS-LRR genes. A YAC-contig was established for one of these mixed clusters. YAC fragmentation experiments revealed the presence of at least five NBS-LRR genes within 200 kb in head-to-tail orientation.
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  • 33
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    Theoretical and applied genetics 98 (1999), S. 1087-1090 
    ISSN: 1432-2242
    Keywords: Key words Quantitative trait loci ; Genetic mapping ; RFLP ; Agronomic characters ; Secale cereale L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Progenies of an F2 mapping population were analyzed for quantitative traits to detect QTLs by using marker information from F2 plants for chromosome 5R. The mapping population was segregating for the major dwarfing gene Ddw1 and the gene Hp1 for hairy peduncle. The only QTL determining plant height was located between HP1 and Ddw1 on the distal part of chromosome 5RL. At the same position a QTL for peduncle length was found, and this trait was closely related to plant height (r=0.895). Since Hp1 and Ddw1 are dominant marker loci, no dominance effect could be estimated. The QTLs for spike length and the number of florets were located near the centromere on 5RL. These two traits were correlated with r=0.824 and showed partial dominance, but these traits were not correlated to plant height and peduncle length. Homoeologous relationships between the QTLs mapped for the first time in rye and those mapped in other Triticeae members are discussed.
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  • 34
    ISSN: 1432-2242
    Keywords: Key words Fusarium head blight ; Scab ; Kernel discoloration ; Black point ; Kernel blight ; Deoxynivalenol (DON) ; RFLP ; Barley
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Resistance to Fusarium head blight (FHB), deoxynivalenol (DON) accumulation, and kernel discoloration (KD) in barley are difficult traits to introgress into elite varieties because current screening methods are laborious and disease levels are strongly influenced by environment. To improve breeding strategies directed toward enhancing these traits, we identified genomic regions containing quantitative trait loci (QTLs) associated with resistance to FHB, DON accumulation, and KD in a breeding population of F4:7 lines using restriction fragment length polymorphic (RFLP) markers. We evaluated 101 F4:7 lines, derived from a cross between the cultivar Chevron and an elite breeding line, M69, for each of the traits in three or four environments. We used 94 previously mapped RFLP markers to create a linkage map. Using composite interval mapping, we identified 10, 11, and 4 QTLs associated with resistance to FHB, DON accumulation, and KD, respectively. Markers flanking these QTLs should be useful for introgressing resistance to FHB, DON accumulation, and KD into elite barley cultivars.
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  • 35
    ISSN: 1432-2242
    Keywords: Key words Cucumis melo ; Molecular markers ; RAPD ; CAPS ; RFLP ; Fusarium oxysporum ; Fusarium resistance ; Marker-assisted selection (MAS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Fusarium wilt, caused by Fusarium oxysporum Schlecht f. sp. melonis Snyder & Hans, is a worldwide soil-borne disease of melon (Cucumis melo L.). Resistance to races 0 and 1 of Fusarium wilt is conditioned by the dominant gene Fom-2. To facilitate marker-assisted backcrossing with selection for Fusarium wilt resistance, we developed cleaved amplified polymorphic sequences (CAPS) and restriction fragment length polymorphisms (RFLP) markers by converting RAPD markers E07 (a 1.25-kb band) and G17 (a 1.05-kb band), respectively. The RAPD-PCR polymorphic fragments from the susceptible line ’Vedrantais’ were cloned and sequenced in order to construct primers that would amplify only the target fragment. The derived primers, E07SCAR-1/E07SCAR-2 from E07 and G17SCAR-1/G17SCAR-2 from G17, yielded a single 1.25-kb fragment (designated SCE07) and a 1.05-kb fragment (designated SCG17) (the same as RAPD markers E07 and G17), respectively, from both resistant and susceptible melon lines, thus demonstrating locus-specific associated primers. Potential CAPS markers were first revealed by comparing sequence data between fragments amplified from resistant (PI 161375) and susceptible (’Vedrantais’) lines and were then confirmed by electrophoresis of restriction endonuclease digestion products. Twelve restriction endonucleases were evaluated for their potential use as CAPS markers within the SCE07 fragment. Three (BclI, MspI, and BssSI) yielded ideal CAPS markers and were subsequently subjected to extensive testing using an additional 88 diverse melon cultigens, 93 and 119 F2 individuals from crosses of ’Vedrantais’ x PI 161375 and ’Ananas Yokneam’×MR-1 respectively, and 17 families from a backcross BC1S1 population derived from the breeding line ’MD8654’ as a resistance source. BclI- and MspI-CAPS are susceptible-linked markers, whereas the BssSI-CAPS is a resistant-linked marker. The CAPS markers that resulted from double digestion by BclI and BssSI are co-dominant. Results from BclI- and MspI-CAPS showed over 90% accuracy in the melon cultigens, and nearly 100% accuracy in the F2 individuals and BC1S1 families tested. This is the first report of PCR-based CAPS markers linked to resistance/susceptibility for Fusarium wilt in melon. The RFLP markers resulting from probing with a clone-derived 1.05-kb SCG17 PCR fragment showed 85% correct matches to the disease phenotype. Both the CAPS and RFLP markers were co-dominant, easier to score, and more accurate and consistent in predicting the melon phenotype than the RAPD markers from which they were derived.
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    Potato research 42 (1999), S. 215-221 
    ISSN: 1871-4528
    Keywords: potato virus Y ; strain differentiation ; RFLP ; potato tuber necrotic ringspot disease ; Solanum tuberosum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A procedure for differentiating PVYNTN from PVYN is described and is based on the unique cleavage of their respective PCR products with strain specific restriction endonucleases. The PCR products corresponding to the 5′ end of the N and NTN strains of PVY were cloned and sequenced, and a restriction map was constructed which included common enzymes that were used for the differentiation of PVYNTN. Unique, single cleavage of PCR products derived from the 5′ end of the PVYNTN genome by Nco I, and that of the N-strain of PVY by Bgl II restriction endonuclease were demonstrated. The specific digestion patterns in polyacrylamide gel were used for the unequivocal differentiation between the N and NTN strains of the virus. Both single and mixed infections were detected in field samples of potatoes using this procedure.
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  • 37
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    Potato research 42 (1999), S. 559-568 
    ISSN: 1871-4528
    Keywords: plastic mulch ; transplanting ; nitrogen ; planting depth ; seed tuber weight ; physiological age ; radiation conversion efficiency ; harvest index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary In many seed potato producing areas, micro- and minitubers are too small for direct planting as seed tubers in the field. Such use of these propagules can, however, be feasible if the crop's growth and development can be advanced. Increasing light interception, harvest index and yield of useable progeny tubers has been proved possible with plastic mulch and pre-planting of small tubers in a greenhouse. High amounts of nitrogen (up to 180 kg ha−1) or deep planting (up to 9 cm) were less effective. Using older or pre-sprouted micro- or minitubers may be beneficial, because this might increase the number of sprouts per mother tuber (and thus stems per plant) or advance the growth of sprouts or stems. However, this would require even more careful management, due to the weakness of these sprouts and stems. Micro- and minitubers should be as large as feasible when used for direct planting in the field.
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  • 38
    ISSN: 1573-5125
    Keywords: denitrification ; nature restoration ; nitrogen ; phosphorus ; riparian areas ; sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Denmark, as in many other European countries, the diffuse losses of nitrogen (N) and phosphorus (P) from the rural landscape are the major causes of surface water eutrophication and groundwater pollution. The export of total N and total P from the Gjern river basin amounted to 18.2 kg ha−1 and 0.63 kg P ha−1 during June 1994 to May 1995. Diffuse losses of N and P from agricultural areas were the main nutrient source in the river basin contributing 76% and 51%, respectively, of the total export. Investigations of nutrient cycling in the Gjern river basin have revealed the importance of permanent nutrient sinks (denitrification and overbank sedimentation) and temporary nutrient storage in watercourses. Temporary retention of N and P in the watercourses thus amounted to 7.2–16.1 g N m−2 yr−1 and 3.7–8.3 g P m−2 yr−1 during low-flow periods. Deposition of P on temporarily flooded riparian areas amounted from 0.16 to 6.50 g P m−2 during single irrigation and overbank flood events, whereas denitrification of nitrate amounted on average to 7.96 kg N yr−1 per running metre watercourse in a minerotrophic fen and 1.53 kg N yr−1 per linear metre watercourse in a wet meadow. On average, annual retention of N and P in 18 Danish shallow lakes amounted to 32.5 g N m−2 yr−1 and 0.30 g P m−2 yr−1, respectively, during the period 1989–1995. The results indicate that permanent nutrient sinks and temporary nutrient storage in river systems represent an important component of river basin nutrient budgets. Model estimates of the natural retention potential of the Gjern river basin revealed an increase from 38.8 to 81.4 tonnes yr−1 and that P-retention increased from −0.80 to 0.90 tonnes yr−1 following restoration of the water courses, riparian areas and a shallow lake. Catchment management measures such as nature restoration at the river basin scale can thus help to combat diffuse nutrient pollution.
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  • 39
    ISSN: 1573-5052
    Keywords: mineralization ; nitrogen ; phosphorus ; salinity ; stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant zonation patterns across New England salt marshes have been investigated for years, but how nutrient availability differs between zones has received little attention. We investigated how N availability, P availability, and plant N status varied across Juncus gerardii, Spartina patens, and mixed forb zones of a Northern New England high salt marsh. We also investigated relationships between several edaphic factors and community production and diversity across the high marsh. P availability, soil salinity, and soil moisture were higher in the mixed forb zone than in the two graminoid zones. NH+ 4-N availability was highest in the J. gerardii zone, but NO− 3-N availability and mid season net N mineralization rates did not vary among zones. Plant tissue N concentrations were highest in the mixed forb zone and lowest in the S. patens zone, reflecting plant physiologies more so than soil N availability. Community production was highest in the J. gerardii zone and was positively correlated with N availability and negatively correlated with soil moisture. Plant species diversity was highest in the mixed forb zone and was positively correlated with P availability and soil salinity. Thus, nutrient availability, plant N status, and plant species diversity varied across zones of this high marsh. Further investigation is needed to ascertain if soil nutrient availability influences or is a result of the production and diversity differences that exist between vegetation zones of New England high salt marshes.
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  • 40
    ISSN: 1573-5125
    Keywords: denitrification ; eutrophication ; estuary ; nitrogen ; sediment-water exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this review of sediment denitrification in estuaries and coastal ecosystems, we examine current denitrification measurement methodologies and the dominant biogeochemical controls on denitrification rates in coastal sediments. Integrated estimates of denitrification in coastal ecosystems are confounded by methodological difficulties, a lack of systematic understanding of the effects of changing environmental conditions, and inadequate attention to spatial and temporal variability to provide both seasonal and annual rates. Recent improvements in measurement techniques involving 15 N techniques and direct N2 concentration changes appear to provide realistic rates of sediment denitrification. Controlling factors in coastal systems include concentrations of water column NO 3 − , overall rates of sediment carbon metabolism, overlying water oxygen concentrations, the depth of oxygen penetration, and the presence/absence of aquatic vegetation and macrofauna. In systems experiencing environmental change, either degradation or improvement, the importance of denitrification can change. With the eutrophication of the Chesapeake Bay, the overall rates of denitrification relative to N loading terms have decreased, with factors such as loss of benthic habitat via anoxia and loss of submerged aquatic vegetation driving such effects.
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  • 41
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    Aquatic ecology 33 (1999), S. 55-64 
    ISSN: 1573-5125
    Keywords: estuaries ; nitrogen ; oxygen depletion ; phosphorus ; regression model ; vertical mixing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In a detailed analysis of oxygen saturation in a shallow Danish estuary it was possible to separate the effect of meteorological forcings (i.e. wind and solar radiation) and nutrient loads on oxygen depletion in bottom water. Regression analysis showed that oxygen saturation tied to nitrogen load rather than to phosphorus load. During summer periods of stratification the oxygen saturation could be attributed to the time elapsed after the onset of stratification and the accumulated nitrogen loading 10 month prior to measurement. Using a 10-year meteorological database and an empirical model it was calculated that a 25% reduction in nitrogen loading would reduce the number of days with severe oxygen depletion (i.e. 〈15% of saturation) by more than 50%.
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  • 42
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    Molecular breeding 5 (1999), S. 561-568 
    ISSN: 1572-9788
    Keywords: wheat ; milling yield ; QTL mapping ; RFLP ; microsatellite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A partial genetic linkage map constructed using 150 single seed descent (SSD) lines generated from a cross between the hexaploid wheat varieties ‘Schomburgk’ and ‘Yarralinka’ was used to identify loci controlling milling yield. Milling yield data were obtained using seed collected from field trials conducted at different sites over two seasons. The estimated broad-sense heritability of milling yield in this population was calculated as 0.48. In the preliminary analysis, two regions were identified on chromosomes 3A and 7D, which were significantly associated with milling yield and accounted for 22% and 19% of the genetic variation, respectively. Bulked segregant analysis in combination with AFLP identified other markers linked to these loci, as well as an additional region on chromosome 5A, which accounted for 19% of the genetic variation. The applicability of these markers as selection tools for breeding purposes is discussed.
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  • 43
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    Molecular breeding 5 (1999), S. 187-195 
    ISSN: 1572-9788
    Keywords: gene mapping ; low nitrogen tolerance ; nitrogen use efficiency ; RFLP ; Zea mays L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Intensively managed crop systems are normally dependent on nitrogen input to maximize yield potential. Improvements in nitrogen- use efficiency (NUE) in crop plants may support the development of cropping systems that are more economically efficient and environment friendly. The objective of this study was to map and characterize quantitative trait loci (QTL) for NUE in a maize population. In preliminary experiments, inbred lines contrasting for NUE were identified and were used to generate populations of F2:3 families for genetic study. A total of 214 F2:3 families were evaluated in replicated trials under high nitrogen (280 kg/ha) and low nitrogen (30 kg/ha) conditions in 1996 and 1997. Analysis of ear-leaf area, plant height, grain yield, ears per plant, kernels number per ear, and kernel weight indicated significant genetic variation among F2:3 families. The heritability of these traits was found to be high (h2=0.57–0.81). The mapping population were genotyped using a set of 99 restriction fragment length polymorphism (RFLP) markers. A linkage map of these markers was developed and used to identify QTL. Between two and six loci were found to be associated with each trait. The correspondence of several genomic regions with traits measured under nitrogen limited conditions suggests the presence of QTL associated with NUE. QTLs will help breeders to improve their maize ideotype of a low-nitrogen efficiency by identifying those constitutive and adaptive traits involved in the expression of traits significantly correlated with yield, such as ear leaf area and number of ears per plant.
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  • 44
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    European journal of plant pathology 105 (1999), S. 61-76 
    ISSN: 1573-8469
    Keywords: core sampling ; foliar nutrient concentrations ; minirhizotrons ; nitrogen ; phosphorus ; potassium ; Rhizolab
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Potato-cyst nematodes (Globodera pallida) cause severe yield losses in potato. Plants infected with potato-cyst nematodes generally have reduced concentrations of nitrogen, phosphorus and potassium in the foliage. This study investigated whether reduced growth of nematode-infected potato is caused by nutrient limitation. Experiments in the field and in containers showed that phosphorus concentration correlated best with total crop biomass at early stages of growth. The role of phosphorus in nematode damage was further investigated in the field and in the Wageningen Rhizolab. The experimental field was infested with potato-cyst nematodes and two levels of nematode density were established by fumigation with a nematicide. Prior applications of calcium carbonate resulted in pHKCl levels of 4.8 and 6.1. Two levels of phosphorus fertiliser were applied: either 0 or 225 kg P ha−1. In the Wageningen Rhizolab, soil of both pH levels from the field was used after treatment with 1 MRad gamma irradiation to kill the nematodes. Subsequently, half of the soil was inoculated with cysts to give a nematode density of 30 viable juveniles per gram of soil. In the field, nine weeks after planting, the total crop biomass ranged from 107 g m−2 for the treatment with nematodes at pHKCl 6.1 without phosphorus fertiliser to 289 g m−2 for the fumigated treatment at pHKCl 4.8 with phosphorus fertiliser. The differences in total biomass for the various treatments were explained by differences in foliar phosphorus concentration. Nematodes induced or aggravated P deficiency and reduced total biomass. This was not the only damage mechanism as at high, non-limiting levels of foliar phosphorus concentration, nematodes still reduced total biomass. In the Wageningen Rhizolab, directly after planting, the number of roots visible against minirhizotrons was reduced by nematodes. However, the increase of root number in the nematode treatment continued longer than in the control, until root number was higher than that of the control. The compensary root growth of the nematode treatment was restricted to the top 30 cm and nematodes reduced rooting depth. High soil pH reduced growth, mainly by reducing the availability of phosphate. Both nematodes and high soil pH reduced nutrient uptake per unit root length. Our results lead us to suggest an interaction between nematodes and soil pH, with nematode damage being higher at pHKCl 6.1 than at pHKCl 4.8.
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  • 45
    ISSN: 1573-868X
    Keywords: Osaka Bay ; sediment ; carbon ; nitrogen ; organic matter ; stable isotope ratio ; terrestrial organic matter ; TOC ; POC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Carbon and nitrogen stable isotope ratios (δ13C and δ15N) of surface sediments were measured within Osaka Bay, in the Seto Inland Sea in Japan, in order to better understand the sedimentation processes operating on both terrestrial and marine organic matter in the Bay. The δ13C and δ15N of surface sediments in the estuary of the Yodo River were less than −23‰ and 5‰ respectively, but increased in the area up to about 10 km from the river mouth. At greater distances they became constant (giving δ13C of about −20‰ and δ15N about 6‰). It can be concluded that large amounts of terrestrial organic matter exist near the mouth of the Yodo River. Stable isotope ratios in the estuary of the Yodo River within 10 km of the river mouth were useful indicators allowing study of the movement of terrestrial organic matter. Deposition rates for total organic carbon (TOC) and total nitrogen (TN) over the whole of the Bay were estimated to be 63,100 ton C/year and 7,590 ton N/year, respectively. The deposition rate of terrestrial organic carbon was estimated to be 13,200 (range 2,000–21,500) ton C/year for the whole of Osaka Bay, and terrestrial organic carbon was estimated to be about 21% (range 3–34) of the TOC deposition rate. The ratio of the deposition rate of terrestrial organic carbon to the rate inflow of riverine TOC and particulate organic carbon (POC) were estimated to be 19% (range 3–31) and 76% (range 12–100), respectively.
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  • 46
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    Water resources management 13 (1999), S. 303-314 
    ISSN: 1573-1650
    Keywords: economics ; irrigation ; nitrogen ; nutrients ; wastewater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: Abstract The optimal wastewater treatment level is affected by costs, hazards and benefits. Lowering the wastewater treatment level decreases fertilization costs because of the increased levels of available nutrients left in the water, and irrigation costs decrease if water prices reflect the lower treatment costs. Agricultural yields and/or prices may decrease according to differences between levels of nutrients needed by crops and those available in wastewater. The present article focuses on determination of monthly optimal treatment levels and of the mix of crops calculated to maximize agricultural incomes, according to farmers' point of view. It does not reflect the national point-view focusing on maximization of net national benefits considering also environmental hazards. The methodology appears in Haruvy (1994) and application will be presented in another article (Haruvy et al., 1999).
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  • 47
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; Zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by Zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high Zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a Zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
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  • 48
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more 15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in 15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
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  • 49
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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  • 50
    ISSN: 1573-515X
    Keywords: Baltic Sea ; cyanobacteria ; estuaries ; grazing ; iron ; lakes ; molybdenum ; nitrogen ; nitrogen fixation ; nitrogen limitation ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Explaining the nearly ubiquitous absence of nitrogen fixation by planktonic organisms in strongly nitrogen-limited estuaries presents a major challenge to aquatic ecologists. In freshwater lakes of moderate productivity, nitrogen limitation is seldom maintained for long since heterocystic, nitrogen-fixing cyanobacteria bloom, fix nitrogen, and alleviate the nitrogen limitation. In marked contrast to lakes, this behavior occurs in only a few estuaries worldwide. Primary production is limited by nitrogen in most temperate estuaries, yet no measurable planktonic nitrogen fixation occurs. In this paper, we present the hypothesis that the absence of planktonic nitrogen fixers from most estuaries is due to an interaction of bottom-up and top-down controls. The availability of Mo, a trace metal required for nitrogen fixation, is lower in estuaries than in freshwater lakes. This is not an absolute physiological constraint against the occurrence of nitrogen-fixing organisms, but the lower Mo availability may slow the growth rate of these organisms. The slower growth rate makes nitrogen-fixing cyanobacteria in estuaries more sensitive to mortality from grazing by zooplankton and benthic organisms. We use a simple, mechanistically based simulation model to explore this hypothesis. The model correctly predicts the timing of the formation of heterocystic, cyanobacterial blooms in freshwater lakes and the magnitude of the rate of nitrogen fixation. The model also correctly predicts that high zooplankton biomasses in freshwaters can partially suppress blooms of nitrogen-fixing cyanobacteria, even in strongly nitrogen-limited lakes. Further, the model indicates that a relatively small and environmentally realistic decrease in Mo availability, such as that which may occur in seawater compared to freshwaters due to sulfate inhibition of Mo assimilation, can suppress blooms of heterocystic cyanobacteria and prevent planktonic nitrogen fixation. For example, the model predicts that at a zooplankton biomass of 0.2 mg l−1, cyanobacteria will bloom and fix nitrogen in lakes but not in estuaries of full-strength seawater salinity because of the lower Mo availability. Thus, the model provides strong support for our hypothesis that bottom-up and top-down controls may interact to cause the absence of planktonic nitrogen fixation in most estuaries. The model also provides a basis for further exploration of this hypothesis in individual estuarine systems and correctly predicts that planktonic nitrogen fixation can occur in low salinity estuaries, such as the Baltic Sea, where Mo availability is greater than in higher salinity estuaries.
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  • 51
    ISSN: 1573-8469
    Keywords: electron microscopy ; molecular identification ; PCR ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During the summer 1996, twelve of twenty-eight leek plants located in a garden near České Budějovice, South Bohemia exhibited symptoms typical of diseases associated with phytoplasmas. In summer 1998 similar symptoms were detected in leek plants in a field used for seed production located in Romagna, North Italy. In both cases the plants were established in the spring of the previous year. Plants showed flower abnormalities: stamen elongation, anther sterility, pistil proliferation, as well as poor, if any, seed production. Phytoplasma-like structures were detected by scanning and transmission electron microscopy in phloem sieve elements in the Czech diseased plants, but not in healthy ones. Nested-PCR amplifications of extracted DNA with phytoplasma-specific oligonucleotide primer pairs confirmed the presence of phytoplasmas in these plants at low concentrations. Restriction fragment length polymorphism analyses of amplified ribosomal sequences allowed the identification of detected phytoplasmas: all the samples from the Czech Republic contained aster yellows related phytoplasmas (16SrI-B) while in the Italian samples aster yellows related phytoplasmas (16SrI-B) together with stolbur related phytoplasmas (16SrXII-A) were identified. This is the first report of detection and identification of a phytoplasma disease of leek in the Czech Republic and Italy.
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  • 52
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    European journal of plant pathology 105 (1999), S. 667-680 
    ISSN: 1573-8469
    Keywords: asexual reproduction ; mating types ; oomycetes ; origin ; RAPD ; RFLP ; population genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phytophthora cinnamomi isolates from South Africa and Australia were compared to assess genetic differentiation between the two populations. These two populations were analysed for levels of phenotypic diversity using random amplified polymorphic DNAs (RAPDs) and gene and genotypic diversity using restriction fragment length polymorphisms (RFLPs). Sixteen RAPD markers from four decanucleotide Operon primers and 34 RFLP alleles from 15 putative loci were used. A few isolates from Papua New Guinea known to posses alleles different from Australian isolates were also included for comparative purposes. South African and Australian P. cinnamomi populations were almost identical with an extremely low level of genetic distance between them (Dm=0.003). Common features for the two populations include shared alleles, low levels of phenotypic/genotypic diversity, high clonality, and low observed and expected levels of heterozygosity. Furthermore, relatively high levels of genetic differentiation between mating type populations (Dm South Africa=0.020 and Dm Australia=0.025 respectively), negative fixation indices, and significant deviations from Hardy–Weinberg equilibrium, all provided evidence for the lack of frequent sexual reproduction in both populations. The data strongly suggest that both the South African and Australian P. cinnamomi populations are introduced.
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  • 53
    ISSN: 1573-5036
    Keywords: ectomycorrhizae ; Eucalyptus regnans ; forest burns ; nitrogen ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to compare the effects on the growth of Eucalyptus regnans seedlings of unheated soil and soil heated to different extents (as indicated by soil colour–bright red or black) in burnt logging coupes, and to separate the effects of heating of the soil on direct nutrient availability and on morphotypes and effectiveness of ectomycorrhizae. Burnt soils were collected from three logging coupes burnt 2, 14 and 25 months previously and unbumt soil from adjacent regrowth forests. Compared to unburnt soil, the early seedling growth was stimulated in black burnt soil from all coupes (burnt 2, 14 and 25 months previously). Seedling growth was generally poor in red burnt soil, especially in soil collected 2 months after burning. However, the concentration of extractable P was extremely high in red burnt soil, especially in soil collected 2 months after burning. In black burnt soil, extractable P was increased in soil 2 months after burning, but not in the soils collected 14 or 25 months after burning. However, both total P content and concentration in seedlings were increased in all collections of black burnt soil. Frequency of ectomycorrhizae was high in seedlings grown in all black burnt soils, but the mycorrhizal mantles were poorly developed in seedlings in black burnt soil collected 2 months after burning. Seedlings were also ectomycorrhizal in red burnt soil, except in soil collected 2 months after burning. Fine root inocula from seedlings grown in black burnt soils collected 14 and 25 months after burning significantly stimulated both seedling growth and P uptake compared with the uninoculated control, whereas the fine root inocula from the seedlings grown in all the other soils did not. These results suggest that, in black burnt soil, both direct nutritional changes and changes in the ectomycorrhizae may contribute to seedling growth promotion after regeneration burns. The generally poor seedling growth in red burnt soils is likely to have been due to N deficiency as the seedlings in these soils were yellow-green and the tissue concentrations of N were significantly lower than in other treatments.
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  • 54
    ISSN: 1573-5060
    Keywords: Bph-1 ; linkage analysis ; mapping ; RAPD ; RFLP ; rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract We report the tagging of a brown planthopper (BPH) resistance gene (Bph–1) in rice using RAPD and RFLP markers. The Korean rice variety ‘Gayabyeo’ has dominant duplicate genes including Bph–1 conferring resistance to biotype 1 of BPH. Bulked segregant RAPD analysis was employed for rapid identification of DNA markers linked to resistance genes. For tagging these two genes, an F2F3 population from a ‘Gayabyeo’ × ‘Nagdongbyeo’ cross was developed and evaluated for BPH resistance. Three bulked DNAs from two groups of homozygous BPH resistant (each for Bph–1 and the other unknown gene) and homozygous susceptible F2 plants were analyzed by RAPD using 140 random oligomers. One primer, OPD–7 yielded a 700-bp fragment that was present in Gayabyeo and resistant F2 plants (homozygous for Bph-1 locus) but absent in Nagdongbyeo and susceptible F2 plants. Cosegregation of this marker with Bph-1 was verified using an F2 population segregating for Bph-1. Chromosomal regions surrounding the Bph-1 were examined with additional RFLP and microsatellite markers on chromosome 12 to define the location of the RAPD marker and Bph-1. Use of this RAPD marker could facilitate early selection of resistant lines for BPH.
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  • 55
    ISSN: 1573-5036
    Keywords: crop residues ; isotope dilution ; 15N ; nitrogen ; organic matter ; pool substitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Experiments were carried out to compare the direct approach for estimating crop N uptake from 15N labelled organic inputs, to two indirect approaches, 15N isotope dilution and A value. In the first experiment soils received 25, 50, 75, or 100 mg N kg soil−1 in the form of Casuarina equisitifolia residues in addition to ammonium sulphate fertiliser, to give a total of 100 mg N kg soil−1 added. This was a cross labelling design, thus two matching sets of treatments, were set up, identical in all but the position of the 15N label. Maize (Zea mays L.) plants were grown in the soils amended with residues for 11 weeks and N derived from residues (Ndfr) estimated using the A-value or the direct approach. The A-value approach appeared to significantly overestimate %Ndfr compared to the direct method. In the second experiment contrasting residues were added to soil, fababean (Vicia faba L. var. minor), alfalfa (Medicago sativa L.), soyabean fixing, (Glycine max (L.) Merrill), soyabean non-fixing, barley (Hordeum vulgare L.) and maize. This was also cross-labelling design, labelled and unlabelled residues were used. Maize plants were grown in these soils for 11 weeks and %Ndfr in the maize plants estimated using 15 N isotope dilution and the direct approach. The 15 N isotope dilution approach also overestimated %Ndfr compared to the direct method in this experiment. Pool substitution appeared to be responsible for the discrepancy between the direct and indirect techniques. It was concluded that 15N isotope dilution and A-value approaches as used in these experiments (i.e where residues and 15N label are added simultaneously) were not appropriate techniques for estimating N derived from organic residues in soils.
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  • 56
    ISSN: 1573-5036
    Keywords: nitrogen ; Prunus ; remobilisation ; storage ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two-year old nectarine trees (Prunus persica, Batsch, var. nectarina, cv. Starkredgold on GF305 rootstock) planted in pots each received five applications of 1.0 g 15N labelled urea either from mid May to mid July (early uptake) or from mid August to the beginning of October (late uptake). All trees were supplied with a corresponding amount of unlabelled urea when they did not receive the labelled N. In autumn, all abscised leaves were collected and during winter randomly selected trees were harvested and divided into main organs. The remaining trees were transplanted into similar pots filled with sand; they received no N fertiliser and were harvested in May to evaluate the remobilisation of N. Total N and 15N abundance were determined in each organ. Nectarine trees took up similar amounts of N in the 'early' and in the 'late' period; however, more labelled nitrogen was recovered in the perennial organs during the winter when trees received the labelled N in the 'late' than in the 'early' period. Some 73–80% of the N present in the dormant trees was stored in the roots, which contained almost twice the amount of labelled N taken up 'late' than that absorbed 'early'. Nitrogen for spring growth was remobilised predominantly from the roots and accounted for some 43–49% of the labelled N recovered in the tree during winter. Results suggest that the nitrogen taken up 'late' in the season is preferentially stored in roots and used by peach trees to sustain new growth the following spring.
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  • 57
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    Plant and soil 212 (1999), S. 207-217 
    ISSN: 1573-5036
    Keywords: legume ; nitrogen ; N2-fixation ; pea ; sulphur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A S-deficient soil was used in pot experiments to investigate the effects of S addition on growth and N2-fixation in pea (Pisum sativum L.). Addition of 100 mg S pot−1 increased seed yield by more than 2-fold. Numbers of pods formed were the most sensitive yield component affected by S deficiency. Sulphur addition also increased the concentration of N in leaves and stems, and the total content of N in the shoots. The amounts of N fixed by pea were determined at four growth stages from stem elongation to maturity, using the 15N dilution technique. Sulphur addition doubled the amount of N fixed at all growth stages. In contrast, leaf chlorophyll content and shoot dry weight were increased significantly by S addition only after the flowering and pod fill stage, respectively. Pea roots were found to have high concentrations of S, reaching approximately 10 mg g−1 dry weight and being 2.6–4.4 times the S concentration in the shoots under S-sufficient conditions. These results suggest that roots/nodules of pea have a high demand for S, and that N2-fixation is very sensitive to S deficiency. The effects of S deficiency on pea growth were likely to be caused by the shortage of N, due to decreased N2-fixation.
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  • 58
    ISSN: 1573-5036
    Keywords: fire ; nitrogen ; phosphorus ; soil nutrient heterogeneity ; tree effects ; tropical dry forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Individual trees are known to influence soil chemical properties, creating spatial patterns that vary with distance from the stem. The influence of trees on soil chemical properties is commonly viewed as the agronomic basis for low-input agroforestry and shifting cultivation practices, and as an important source of spatial heterogeneity in forest soils. Few studies, however, have examined the persistence of the effects of trees on soil after the pathways responsible for the effects are removed. Here, we present evidence from a Mexican dry forest indicating that stem-related patterns of soil nutrients do persist following slash-and-burn removal of trees and two years of cropping. Pre-disturbance concentrations of resin extractable phosphorus (P), bicarbonate extractable P, NaOH extractable P, total P, total nitrogen (N) and carbon (C), KCl extractable nitrate (NO3 -), and net N mineralization and nitrification rates were higher in stem than dripline soils under two canopy dominant species of large-stemmed trees with contrasting morphologies and phenologies (Caesalpinia eriostachys Benth. and Forchhammeria pallida Liebm.). These stem effects persisted through slash burning and a first growing season for labile inorganic and organic P, NaOH inorganic P, and plant-available P, and through a second growing season for labile organic P, NaOH organic P, and plant-available P. While stem effects for extractable NO3 -, net nitrification rates, total N and C disappeared after felling and slash burning, these stem effects returned after the first growing season. These results support the view that tree-influenced patterns of soil nutrients do persist after tree death, and that trees contribute to the long-term spatial heterogeneity of forest soils.
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  • 59
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    Plant and soil 212 (1999), S. 173-181 
    ISSN: 1573-5036
    Keywords: nitrogen ; phosphatase activity ; phosphorus ; protease activity ; soil microbial biomass ; substrate-induced respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Estimating in situ N and P status of the soil microbiota is complicated because microbiological features reflect potentials rather than field conditions. Complementary microbiological assays were, therefore, combined to evaluate the N and P requirement of the microbiota in seven agricultural, grassland and forest topsoils of the Bornhöved Lake district as follows: (i) the sensitivity of the substrate-induced respiration (SIR) to supplemental addition of N and P was monitored during microbial growth and (ii) soil protease and phosphatase activities were analysed and related to soil mass and microbial biomass content. Nitrogen addition increased the maximal SIR rate in all except one soil indicating that the growth of organisms is restricted by this element when easily degradable C source is present. Supplemental N (and in some cases also P) retarded the respiratory response within the first 24 h which suggests microbial sensitivity and/or greater anabolic efficiency. With additional N the maximal SIR rate was most strongly enhanced in topsoils of the beech forest and the dystric alder forest. Thus, the microbial growth in these soils that were below litter horizons seems to be mostly restricted by N. Supplemental P positively affected respiratory response of soils under monoculture, wet grassland and dystric alder forest. In the dystric alder forest soil, high rates of alkaline and unbuffered phosphatase activity were observed when activity was related to either soil mass or microbial biomass content. The data of proteolytic and phospholytic enzymes are discussed with reference to nutrient deficiency and microbial strategy for N and P adsorption.
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  • 60
    ISSN: 1573-5036
    Keywords: effluent ; leaching ; 15N isotope ; nitrogen ; pasture ; uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this study was to compare the N leaching loss and pasture N uptake from autumn-applied dairy shed effluent and ammonium fertilizer (NH4Cl) labeled with 15N, using intact soil lysimeters (80 cm diameter, 120 cm depth). The soil used was a sandy loam, and the pasture was a mixture of perennial ryegrass (Lolium perenne) and white clover (Trifolium repens). The DSE and NH4Cl were applied twice annually in autumn (May) and late spring (November), each at 200 kg N ha-1. The N applied in May 1996 was labeled with 15N. The lysimeters were either spray or flood irrigated during the summer. The autumn-applied DSE resulted in lower N leaching losses compared with NH4Cl. However, the N applied in the autumn had a higher potential for leaching than N applied in late spring. Between 4.5–8.1% of the 15N-labeled mineral N in the DSE and 15.1–18.8% of the 15N-labeled NH4Cl applied in the autumn were leached within a year of application. Of the annual N leaching losses in the DSE treatments (16.0–26.9 kg N ha-1), a fifth (20.3–22.9%) was from the mineral N fraction of the DSE applied in the autumn, with the remaining larger proportion from the organic fraction of the DSE, soil N and N applied in spring. In the NH4Cl treatments, more than half (53.8–64.8%) of the annual N leaching loss (55.9–57.6 kg N ha-1) was derived from the autumn-applied NH4Cl. DSE was as effective as NH4Cl in stimulating pasture production. Since only 4.4–4.5% of the annual herbage N uptake in the DSE treatment and 12.3–13.3% in the NH4Cl treatment were derived from the autumn-applied mineral N, large proportions of the annual herbage N uptake must have been derived from the N applied in spring, the organic N fraction in the DSE, soil N and N fixed by clover. The recoveries of 15N in the herbage were similar between the DSE and the NH4Cl treatments, but those in the leachate were over 50% less from the DSE than from the NH4Cl treatment. The lower leaching loss of 15N in the DSE treatment was attributed to the stimulated microbial activities and increased immobilization following the application of DSE.
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  • 61
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    Hydrobiologia 408-409 (1999), S. 375-387 
    ISSN: 1573-5117
    Keywords: eutrophication ; multi-lake studies ; phosphorus ; nitrogen ; chlorophyll-a ; transparency ; zooplankton ; macrophytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Monitoring data obtained from 231 freshwater lakes and ponds in the Netherlands, covering the period 1980–1996, were used to analyse the relationships between (a) transparency and chlorophyll-a, and the effect of system characteristics on this relationship, (b) chlorophyll-aand nutrient concentrations, and the effect of biological variables and (c) nutrient concentrations and nutrient loading. (a) Chlorophyll-aimposes a maximum on water transparency, but deviations from this maximum can be large. Reducing chlorophyll-a, therefore, does not guarantee a sufficient improvement of transparency. Soil type and the average depth of a lake were shown to influence the relationship between chlorophyll-aand transparency. (b) The maximum ratios of both chlorophyll-a: total-P and chlorophyll-a: total-N were higher in systems dominated by filamentous cyanobacteria than in systems dominated by other algae, indicating the efficiency of the former group with respect to nutrients. In systems with an areal coverage with submersed macrophytes above 5%, concentrations of chlorophyll-aand nutrients were lower than in systems with lower coverages. The ratios between chlorophyll-aand nutrients were lower at coverages larger than 10%. This indicates both bottom-up and top-down control of algae by macrophytes. Grazing pressure by zooplankton was also found to lower the chlorophyll-a: nutrient ratios. (c) System specific linear relationships were found between the average concentrations of total-P and total-N in the incoming water and the summer mean concentration in the lake. This allows the assessment of admissible loads for individual lakes, with narrower confidence limits compared to traditional relationships based on combined data from many lakes. From the analysis, it is concluded that the chain of relationships from nutrient loading to transparency is complex, and depends on biological variables as well as system characteristics.
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  • 62
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    Biogeochemistry 44 (1999), S. 93-118 
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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  • 63
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1× 104 kg nitrogen and 3.91×104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7×104 kg (676 kg/ha) nitrogen and 3.88×104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55×104 kg nitrogen and 0.40×104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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  • 64
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/1) and lowest in bare plots in the shrubland (0.55 mg/1). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands — consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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  • 65
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; pore water ; macrophyte ; floodplain ; Paraná River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Inorganic nitrogen and soluble reactive phosphate (o-P) concentrations were measured in the water of a marsh and in its interstitial water at two sites, and in the river water of a floodplain marsh of the Lower Paraná River. These values were compared with the N and P concentration in sediments and macrophyte biomass in order to assess nutrient availability, fate and storage capacity. High variability was found in the interstitital water using a 1 cm resolution device. Nitrate was never detected in the pore water. Depth averaged NH4 + concentrations in the upper 30 cm layer often ranged from N = 1.5 to 1.8 mg l-1, but showed a pronounced minimum (0.5–0.7 mg l-1), close to (March 95), or relatively soon after (May 94) the end of the macrophyte growing season. Soluble phosphate showed a large variation between P = 0.1–1.1 mg l-1 without any discernible seasonal pattern. NH4 + depletion in the pore water concentration and low N/P ratios (3.7 by weight) within the macrophyte biomass at the end of the growing period suggest that available N limits plant growth. NH4 + and o-P concentrations were 35 and 7 times higher, respectively, in the pore water than in the overlying marsh, suggesting a permanent flux of nutrients from the sediments. o-P accumulate in the marsh leading to higher concentrations than in the incoming river. NH4 + did not accumulate in the marsh, and no significant differences were observed between the river and the marsh water, while the NO3 - contributed by the river water was depleted within the marsh, caused probably by coupled nitrification-denitrification at the sediment–water interface. Although an order of magnitude smaller, the pore water pool can supply enough nutrients to build up the macrophyte biomass pool, but only if a fast turnover is attained. The Paraná floodplain marsh retains a large amount of nutrients being stored mainly in the sediment compartment.
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  • 66
    ISSN: 1573-5117
    Keywords: shallow lake ; nutrient loading ; retention ; nitrogen ; phosphorus ; release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The shallow (mean depth 4.9 m), polymictic and eutrophic lake Müggelsee was highly loaded with phosphorus (6 gP m-2a-1) and nitrogen (170 gN m-2a-1) by the river Spree up to the end of the 1980s. Annual load declined by 40–50% during the last years (1991–97). Phosphorus retention fluctuated strongly during the seasonal cycle between −200 and +100 kgP d-1and from year to year between −44% and + 26% of the P import. At the end of the eighties, the P retention capacity of the sediment was exceeded and Müggelsee became a source of phosphorus. The lake regained its ability to retain P in the sediments after external load reduction in the 1990s. However, the internal load of P reached the level of the external one. The release of P during summer was strongly related to the import of nitrate. On long-term average (1979–1997), less than 1% of the P input was retained in Müggelsee. About 24% of the nitrogen load were removed in the lake on annual mean. This rate decreased during the last years.
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  • 67
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    Hydrobiologia 395-396 (1999), S. 389-401 
    ISSN: 1573-5117
    Keywords: legislation ; eutrophication ; phosphorus ; nitrogen ; wildlife conservation ; SSSI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There is no single piece of legislation which comprehensively addresses the problem of eutrophication of freshwater lakes. An examination is made of the extent to which national and EU laws applicable in England and Wales may be used to reduce phosphorus inputs to eutrophicated lakes. This case study is then used to outline the shortcomings of existing legislation and the future challenges for lake eutrophication control. Applicable legislation may be divided into that relating to nature conservation, to water quality and to agricultural extensification. Nature conservation laws are applicable, in that lakes designated as Sites of Special Scientific Interest (SSSIs), are theoretically safeguarded from degradation. The main limitation of the SSSI system lies in the boundary definition process under which, as a rule, no other category of legally protected land may be designated. Thus, the use of surrounding buffer land to protect water quality at the catchment level is generally precluded. The introduction of consultation areas around SSSIs of international importance under the EU Directive on Habitats is unlikely to alleviate the problem, since the area involved remains minimal compared to the extent of the majority of catchments. Intensive agricultural practices are responsible for significant nutrient enrichment of rivers and lakes, so that legislation aimed at extensification is also relevant. Examples of agricultural extensification include the Environrnentally Sensitive Areas programme and various options available for Set-Aside land. However, the prime purpose of such initiatives is the alleviation of surplus and budgetary problems and, as such, they fall short of a fully integrated approach to the ecological management of farmland. Nutrient enrichment is, essentially, a water quality issue, but policy and legislation in this area are not yet sufficiently developed to address the problem comprehensively. The current regulatory process for water quality carries the potential to work comparatively well for point sources under the system of consents to discharge. This potential is limited, however, by the paucity of information available on ecologically acceptable concentrations of phosphorus in discharges. In addition, the consents system is not constructed to deal effectively with diffuse agricultural losses of phosphorus, since, unlike point sources, these tend to arise from the cumulative effect of many activities. The main legislative challenge for lake eutrophication control lies in the area of diffuse agricultural losses of phosphorus. In this respect, experience in the U.S.A. reveals that the use of comprehensive and catchment-wide ‘Best Management Practices’ is capable of producing significant water quality improvements, providing that some degree of mandatory compliance is incorporated.
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  • 68
    ISSN: 1573-5117
    Keywords: Integrated lake management ; biomanipulation ; lake recovery ; phosphorus ; nitrogen ; eutrophication ; restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The majority of Danish lakes are highly eutrophic due to high nutrient input from domestic sources and agricultural activities. Reduced nutrient retention, and more rapid removal, in catchments as a result of agricultural drainage of wetlands and lakes and channelisation or culverting of streams also play a role. Attempts have recently been made to reduce nutrient loading on lakes by intervening at the source level and by improving the retention capacity of catchment areas. The former measures include phosphorus stripping and nitrogen removal at sewage works, increased use of phosphate-free detergents, and regulations concerning animal fertiliser storage capacity, fertiliser application practices, fertilisation plans and green cover in winter. In order to improve nutrient retention capacity of catchments, wetlands and lakes have been re-established and channelised streams have been remeandered. In addition, cultivation-free buffer strips have been established alongside natural streams and there has been a switch to manual weed control. These measures have resulted in a 73% reduction of the mean total phosphorus concentration of point-source polluted streams since 1978; in contrast, there has been no significant change in the total nitrogen concentration. Despite the major reduction in stream phosphorus concentrations, lake water quality has often not improved. This may reflect a too high external or internal phosphorus loading or biological resistance. Various physico-chemical restoration measures have been used, including dredging and oxidation of the hypolimnion with nitrate and oxygen. Biological restoration measures have been employed in 17 Danish lakes. The methods include reducing the abundance of cyprinids, stocking with 0+ pike ( Esox lucius) to control 0+ cyprinids, and promoting macrophyte recolonization by protecting germinal submerged macrophyte beds against grazing waterfowl and transplanting out macrophyte shoots. In several lakes, marked and long-lasting improvements have been obtained. The findings to date indicate that fish manipulation has a long-term effect in shallow lakes, providing nutrient loading is reduced to a level so low as to ensure an equilibrium lake water phosphorus concentration of less than 0.05–0.1 mg phosphorus l−1. If nitrogen loading is very low, however, positive results may be obtained at higher phosphorus concentrations. Macrophyte refuges and transplantation seem to be the most successful as restoration measures in the same nutrient-phosphorus regime as fish manipulation.
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  • 69
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    Biogeochemistry 44 (1999), S. 93-118 
    ISSN: 1573-515X
    Keywords: Everglades National Park ; mangrove soils ; organic matter ; nitrogen ; phosphorus ; sedimentation ; simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The distribution and accumulation of organic matter, nitrogen (N) and phosphorus (P) in mangrove soils at four sites along the Shark River estuary of south Florida were investigated with empirical measures and a process-based model. The mangrove nutrient model (NUMAN) was developed from the SEMIDEC marsh organic matter model and parameterized with data from mangrove wetlands. The soil characteristics in the four mangrove sites varied greatly in both concentrations and profiles of soil carbon, N and P. Organic matter decreased from 82% in the upstream locations to 30% in the marine sites. Comparisons of simulated and observed results demonstrated that landscape gradients of soil characteristics along the estuary can be adequately modeled by accounting for plant production, litter decomposition and export, and allochthonous input of mineral sediments. Model sensitivity analyses suggest that root production has a more significant effect on soil composition than litter fall. Model simulations showed that the greatest change in organic matter, N, and P occurred from the soil surface to 5 cm depth. The rapid decomposition of labile organic matter was responsible for this decrease in organic matter. Simulated N mineralization rates decreased quickly with depth, which corresponded with the decrease of labile organic matter. The increase in organic matter content and decrease in soil bulk density from mangrove sites at downstream locations compared to those at upstream locations was controlled mainly by variation in allochthonous inputs of mineral matter at the mouth of the estuary, along with gradients in mangrove root production. Research on allochthonouns sediment input and in situ root production of mangroves is limited compared to their significance to understanding nutrient biogeochemistry of these wetlands. More accurate simulations of temporal patterns of nutrient characteristics with depth will depend on including the effects of disturbance such as hurricanes on sediment redistribution and biomass production.
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  • 70
    ISSN: 1573-515X
    Keywords: Chaohu Lake ; chemical fertilizer ; cycling ; denitrification ; multipond system ; nitrogen ; nutrient budget ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 × 104 kg nitrogen and 3.91 × 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 × 104 kg (676 kg/ha) nitrogen and 3.88 × 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 × 104 kg nitrogen and 0.40 × 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture. The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.
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  • 71
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m−2 yr−1 were made toSphagnum magellanicurn cores at two-week intervalsin situ at four sites across Europe, i.e. Lakkasuo (Finland). Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N∶P ratio 68) and greatest in Moidach More (N∶P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4 + in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3 − were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition bySphagnum mosses.
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  • 72
    ISSN: 1573-515X
    Keywords: N15 ; nitrogen ; nutrient cycling ; plants ; stable isotopes ; soil ; temperate forest ; tropical forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Several lines of evidence suggest that nitrogen in most tropical forests is relatively more available than N in most temperate forests, and even that it may function as an excess nutrient in many tropical forests. If this is correct, tropical forests should have more open N cycles than temperate forests, with both inputs and outputs of N large relative to N cycling within systems. Consequent differences in both the magnitude and the pathways of N loss imply that tropical forests should in general be more15N enriched than are most temperate forests. In order to test this hypothesis, we compared the nitrogen stable isotopic composition of tree leaves and soils from a variety of tropical and temperate forests. Foliar δ15N values from tropical forests averaged 6.5‰ higher than from temperate forests. Within the tropics, ecosystems with relatively low N availability (montane forests, forests on sandy soils) were significantly more depleted in15N than other tropical forests. The average δ15N values for tropical forest soils, either for surface or for depth samples, were almost 8‰ higher than temperate forest soils. These results provide another line of evidence that N is relatively abundant in many tropical forest ecosystems.
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  • 73
    ISSN: 1573-515X
    Keywords: estuaries ; lakes ; marine ; nitrogen ; phosphorus ; rivers ; streams ; temperate ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Published data and analyses from temperate and tropical aquatic systems are used to summarize knowledge about the potential impact of land-use alteration on the nitrogen biogeochemistry of tropical aquatic ecosystems, identify important patterns and recommend key needs for research. The tropical N-cycle is traced from pre-disturbance conditions through the phases of disturbance, highlighting major differences between tropical and temperate systems that might influence development strategies in the tropics. Analyses suggest that tropical freshwaters are more frequently N-limited than temperate zones, while tropical marine systems may show more frequent P limitation. These analyses indicate that disturbances to pristine tropical lands will lead to greatly increased primary production in freshwaters and large changes in tropical freshwater communities. Increased freshwater nutrient flux will also lead to an expansion of the high production, N- and light-limited zones around river deltas, a switch from P- to N-limitation in calcareous marine systems, with large changes in the community composition of fragile mangrove and reef systems. Key information gaps are highlighted, including data on mechanisms of nutrient transport and atmospheric deposition in the tropics, nutrient and material retention capacities of tropical impoundments, and N/P coupling and stoichiometric impacts of nutrient supplies on tropical aquatic communities. The current base of biogeochemical data suggests that alterations in the N-cycle will have greater impacts on tropical aquatic ecosystems than those already observed in the temperate zone.
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  • 74
    ISSN: 1573-5168
    Keywords: adenosine triphosphate ; fertility ; nitrogen ; salmonid ; semen ; spermatocrit ; viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adenosine triphosphate (ATP) levels in sperm from chinook salmon (Oncorhynchus tshawytscha) were found to be 12.1±1.9 pmol ATP per 106 sperm cells (mean±SEM, n=18). Sperm were stored at 0–2 °C for up to 72 h under 100, 21, and 0% O2. Changes in sperm ATP content of samples maintained under 100 and 21% O2 were indistinguishable, decreasing to 50% of initial values after 72 h. ATP levels of sperm stored under 0% O2 decreased to 10% of initial values within 8 h and remained unchanged throughout the following 64 h. The initial percent of living sperm (sperm viability) was 94.7±1.7% (mean±SEM, n=12) and was unaltered at 24 h under all O2 tensions. At 72 h, sperm viability remained unchanged under 21% O2 and had decreased by 20% under 100% O2 and by 30% under 0% O2. Therefore, reductions in sperm ATP levels could not be attributed to cell lysis, as viability decreased only modestly over these durations. Fertilizing ability correlated positively with sperm ATP levels. Spermatocrit values increased by 20% for the samples maintained under 100 and 21% O2 after 72 h. However, a 20% increase in spermatocrit occurred within 24 h in samples maintained under 0% O2, rising 70% after 72 h under 0% O2. These data indicate that chinook sperm ATP (1) can be altered and manipulated without significant loss of viability, (2) is positively associated with fertilization, and (3) probably plays a role in sperm packing and cell flexibility.
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  • 75
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 - , SO 4 2 , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4 and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9 μmol d-1 g-1 dry soil. Methane production started after 2 to 87 days and became constant after about 38--68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08 μmol d-1 g-1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30 μmol d-1 g-1 and 0.02 and 0.28 μmol d-1 g-1, respectively. Within the 120 d of anaerobic incubation only 6--17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61--100% CO2, 〈0.1--35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r = 0.891) and total CH4 produced (r = 0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
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  • 76
    ISSN: 1573-515X
    Keywords: acetate ; carbon dioxide ; hydrogen ; methanogenesis ; iron ; organic carbon ; nitrogen ; redox balance ; rice paddy soil ; sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The potentials for sequential reduction of inorganic electron acceptors and production of methane have been examined in sixteen rice soils obtained from China, the Philippines, and Italy. Methane, CO2, Fe(II), NO 3 − , SO 4 2− , pH, Eh, H2 and acetate were monitored during anaerobic incubation at 30 °C for 120 days. Based on the accumulation patterns of CO2 and CH4, the reduction process was divided into three distinct phases: (1) an initial reduction phase during which most of the inorganic electron acceptors were depleted and CO2 production was at its maximum, (2) a methanogenic phase during which CH4 production was initiated and reached its highest rate, and (3) a steady state phase with constant production rates of CH4. and CO2. The reduction phases lasted for 19 to 75 days with maximum CO2 production of 2.3 to 10.9μmol d−1 g−1 dry soil. Methane production started after 2 to 87 days and became constant after about 38–68 days (one soil 〉120 days). The maximum CH4 production rates ranged between 0.01 and 3.08μmol d−1 g−1. During steady state the constant CH4 and CO2 production rates varied from 0.07 to 0.30μmol d−1 g−1 and 0.02 and 0.28μmol d−1 g−1, respectively. Within the 120 d of anaerobic incubation only 6–17% of the total soil organic carbon was released into the gas phase. The gaseous carbon released consisted of 61–100% CO2, 〈0.1–35% CH4, and 〈5% nonmethane hydrocarbons. Associated with the reduction of available Fe(III) most of the CO2 was produced during the reduction phase. The electron transfer was balanced between total CO2 produced and both CH4 formed and Fe(III), sulfate and nitrate reduced. Maximum CH4 production rate (r=0.891) and total CH4 produced (r =0.775) correlated best with the ratio of soil nitrogen to electron acceptors. Total nitrogen content was a better indicator for “available” organic substrates than the total organic carbon content. The redox potential was not a good predictor of potential CH4 production. These observations indicate that the availability of degradable organic substrates mainly controls the CH4 production in the absence of inorganic electron acceptors.
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  • 77
    ISSN: 1573-1618
    Keywords: CERES ; wheat ; soil moisture ; nitrogen ; variability ; precision agriculture ; spatial
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Crop growth modelling techniques were used to investigate the performance of a wheat crop over a range of weather conditions, nitrogen application rates and soil types. The data were used to predict long term benefits of using spatially variable fertilizer application strategies where fertilizer application rate was matched to the soil type, against a strategy of uniform fertilizer application. The model was also run with modified soil properties to determine the importance of soil moisture holding capacity in the variability of crop yield. It was found that the benefits of spatially variable nitrogen management when fertilizer was applied at the beginning of the season were modest on average. The range of results for different weather conditions was much greater than the average benefit. A large proportion of the variability of crop performance between soil types could be explained by differing soil moisture holding capacity. Devising techniques for managing this variability was concluded to be important for precision farming of cereals.
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  • 78
    ISSN: 1573-0867
    Keywords: acidification ; ANE ; ANR ; calcium ammonium nitrate ; cattle slurry ; dilution ; grassland ; nitric acid ; nitrogen ; residual effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Acidification of cattle slurry with nitric acid to pH 4.5 was studied on experimental dairy farms in the Netherlands as a measure to reduce ammonia losses. This paper presents the results of two field experiments, carried out to assess the utilization of nitrogen (N) from nitric acid treated cattle slurry following surface application to grassland. Three aspects were studied: (i) the utilization of N from nitric acid treated cattle slurry following a single surface application to grassland; (ii) the effects of multiple applications of nitric acid treated cattle slurry on N utilization, residual inorganic N in the soil and sward quality; and (iii) the residual effects of nitric acid treated slurry on DM and N yield. In these experiments undiluted acidified slurry (UAS) and diluted acidified slurry (DAS) were compared with calcium ammonium nitrate (CAN). Apparent N recoveries (ANR) and apparent N efficiencies (ANE) were calculated on the basis of inorganic N in applied fertilizer and slurries. Following single applications of UAS and CAN on the sward on the clay soil, the average ANR values of UAS and CAN were 0.74 and 0.75 kg kg-1, respectively. The average ANE values of UAS and CAN were 30.3 and 29.5 kg DM per kg N, respectively. Single applications of DAS and CAN on the sandy soil resulted in average ANR values of 0.65 and 0.84 kg kg-1 and average ANE values of 24.1 and 29.2 kg DM per kg N for DAS and CAN, respectively. On average, the direct ANR values after four successive applications of CAN, UAS or DAS were 0.82, 0.82 and 0.74 kg kg-1, respectively and the direct ANE values were 28.4, 27.8 and 27.0 kg DM per kg N. On the sandy soil, the amount of residual inorganic N in the soil after the 4th cut increased with increasing rates of inorganic N application, with a slightly higher amount on plots treated with acidified slurry than on plots fertilized with CAN. On the clay soil, the amount of residual inorganic N was not affected by N application rate nor N source. On average, the residual ANR values, in the unfertilized 5th and 6th cuts, of CAN, UAS or DAS were 0.08, 0.10 and 0.09 kg kg-1, respectively and the residual ANE values were 2.7, 3.3 and 3.0 kg DM per kg N. It was concluded that nitric acid treated cattle slurry is an effective N fertilizer on grassland and that the residual effect of nitric acid treated cattle slurry is only marginally higher than that of CAN. Repeated applications of nitric acid treated cattle slurry did not affect sward composition.
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  • 79
    ISSN: 1573-0867
    Keywords: carbon balance ; daily irrigation and fertilisation ; minirhizotrons ; nitrogen ; Phalaris arundinacea ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Biomass and nitrogen in the roots, rhizomes, stem bases and litter of reed canarygrass (Phalaris arundinacea L.) were repeatedly estimated by soil coring, and root growth dynamics of this potential energy crop was studied for two years using minirhizotrons. Results are discussed in relation to above-ground biomass and nitrogen fertilisation. Five treatments were used: C0, unfertilised control; C1, fertilised with solid N fertiliser in spring; I1, irrigated daily, fertilised as in C1; IF1 , irrigated as I1 and fertilised daily through a drip-tube system; IF2, as in IF1 but with higher N fertiliser rates. Biomass of below-ground plant parts of reed canarygrass increased between the first and second years. Up to 50% of total plant biomass and nitrogen were recovered below-ground. The highest proportions were found in C0. The calculated annual input via root turnover ranged between 80 and 235 g m-2. In absolute terms, up to 1 kg and 10 g m-2 of biomass and nitrogen, respectively, were found in below-ground plant fractions. High inputs of stubble and accumulated below-ground biomass will occur when the ley is ploughed, which will result in a highly positive soil carbon balance for this crop in comparison with that of conventional crops such as cereals.
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  • 80
    ISSN: 1573-0867
    Keywords: chickpea ; marginal soils ; nitrogen ; protein content ; Rhizobium ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A field experiment was carried out for two consecutive seasons 1994/95 and 1995/96 at ElRwakeeb (a sandy clay loam) to study the effect of Rhizobium sp. (Cicer) inoculation and N fertilization on six chickpea cultivars (Baladi, Gabel marra, NEC 25–27, NEC 2010, ILC 1919, and Flip 85–108). Plants were either inoculated with three Rhizobium sp. (Cicer) strains (TAL 480, TAL 620 and TAL 1148) separately, or N fertilized (50 kg N ha-1). The results of the two seasons indicated the absence of infective strains for chickpea in the soil. Rhizobium inoculation or N fertilization significantly increased the total nodule number per plant, 100 seed weight, yield and protein content of seeds. The results indicated that the three Rhizobium strains are infective and effective in nitrogen fixation. Inoculation with Rhizobium strain TAL 1148 resulted in a significant increment in most of the parameters studied, compared to other strains and untreated control. Cultivar ILC 1919 was the best yielding cultivar, whereas, cultivar NEC 2010 contained the highest protein content, however cultivar Gabel marra showed the highest amount of protein due to inoculation or N fertilization, in the two seasons. Inoculation with Rhizobium strain TAL 1148 increased yield by 72 and 70%, whereas, 50 kg N ha-1 increased it by 70 and 69% in the first and second seasons, respectively. The amounts of protein accumulated (kg ha-1) due to N or Rhizobium inoculation were determined for all cultivars. The results obtained from the inoculation were comparable to those of 50 kg N ha-1.
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  • 81
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    Agroforestry systems 45 (1999), S. 215-244 
    ISSN: 1572-9680
    Keywords: biodiversity ; disturbance ; nitrogen ; phosphorus ; resilience ; resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Nutrient and hydrologic cycles in harvested native forests in southern Australia are largely balanced. For example, we have little or no evidence of any decline in nutrient capital or availability in harvested forests. Short-term and small-scale reductions in evapotranspiration due to loss of leaf area after harvesting are adequately balanced at the landscape scale by large areas of regenerating or older-age forest. In contrast, agricultural systems on similar soils are a) dependent on large inputs of fertilisers to maintain growth and b) frequently subject to increasing salinity and waterlogging or other forms of degradation. The large-scale replacement of long-lived communities of perennial and often deep- rooting native species with annual crops or other communities of shallow-rooting species might be better managed within the framework of knowledge developed from studies of native plant communities. However, application of such a mimic concept to systems of low natural productivity is limited when agricultural systems require continued high productivity. Nonetheless, the mimic concept may help in developing sustainable management of agriculture on marginal lands, and contribute to the nutritional resilience of agroecosystems. Relevant characteristics for mimic agroecosystems in south western Australia include: high species diversity, diversity of rooting attributes, utilisation of different forms of nutrients (especially of N and P) in space and time, and the promotion of practices which increase soil organic matter content.
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  • 82
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    Biodegradation 10 (1999), S. 43-50 
    ISSN: 1572-9729
    Keywords: biodegradation ; nitrogen ; nutrients ; phenanthrene ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phenanthrene mineralization rates were found to vary widely among four soils; differences in soil nutrient levels was one hypothesis to explain this variation. To test this hypothesis, phenanthrene mineralization rates were measured in these soils with, and without, added nitrogen and phosphorus. Mineralization rates either remained unchanged or were depressed by the addition of nitrogen and phosphorus. Phenanthrene degradation rates remained unchanged in the soil which had the highest indigenous levels of nitrogen and phosphorus and which showed the largest increase in phosphorus levels after nutrients were added. The soils in which degradation rates were depressed had lower initial phosphorus concentrations and showed much smaller or no measurable increase in phosphorus levels after nutrients were added to the soils. To understand the response of phenanthrene degradation rates to added nitrogen and phosphorus, it may be necessary to consider the bioavailability of added nutrients and nutrient induced changes in microbial metabolism and ecology.
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  • 83
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    International journal of thermophysics 20 (1999), S. 867-876 
    ISSN: 1572-9567
    Keywords: dilute mixtures ; high pressure ; high-resolution Raman spectroscopy ; line width ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Previous investigations have revealed a considerable difference between the spectral behavior of a molecule in a pure substance and that in a mixture. To gain more insight into the influence of the intermolecular interaction and of the mass of the molecules, we performed high-resolution measurements of the linewidths and peak positions of the vibrational Raman spectrum of pure nitrogen, nitrogen in argon, and nitrogen in helium. The research was carried out at room temperature and at pressures up to the melting line. It turns out that, in contrast with expectation, the linewidth as well as the frequency shift is essentially the same for pure nitrogen as for nitrogen diluted in argon, although both the mass and the potential well depth are quite different. The experimental results show the same tendency as recent computer simulations.
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  • 84
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    Agroforestry systems 45 (1999), S. 159-185 
    ISSN: 1572-9680
    Keywords: decomposition ; environmental monitoring ; fertiliser ; mineralisation ; nitrogen ; pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil organisms play principal roles in several ecosystem functions, i.e. promoting plant productivity, enhancing water relations, regulating nutrient mineralisation, permitting decomposition, and acting as an environmental buffer. Agricultural soils would more closely resemble soils of natural ecosystems if management practices would reduce or eliminate cultivation, heavy machinery, and general biocides; incorporate perennial crops and organic material; and synchronise nutrient release and water availability with plant demand. In order to achieve these goals, research must be completed to develop methods for successful application of organic materials and associated micro-organisms, synchronisation of management practices with crop and soil biota phenology, and improve our knowledge of the mechanisms linking species to ecosystem processes.
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  • 85
    ISSN: 1573-5060
    Keywords: C-banding ; chromosome additions ; chromosome substitution ; Elymus tsukushiense ; homoeology ; in situ hybridization ; RFLP ; Roegneria kamoji ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Elymus tsukushiense Honda (syn. Roegneria kamoji C. Koch) (2n = 6x = 42, StsStsHtsHtsYtsYts) is a hexaploid species, distantly related to bread wheat Triticum aestivum L. em Thell (2n = 6x = 42, AABBDD). Apart from the delineation of evolutionary relationships, this species is a potential source of resistance to scab, a devastating disease of wheat caused by Fusarium graminearum Schw. A standard C-banded karyotype was established identifying all 21 chromosome pairs of E. tsukushiense. By using C-banding and genomic in situ hybridization analyses, three wheat-E. tsukushiense chromosome addition lines, one ditelosomic addition line, and one disomic substitution line were identified in BC2 progenies from wheat × E. tsukushiense hybrids. Twenty DNA markers specific for the seven homoeologous groups of the Triticeae were used to determine the homoeology of the added E. tsukushiense chromosomes. The E. tsukushiense chromosomes in the addition lines NAU702, NAU703, and NAU701 were identified as belonging to homoeologous groups 1, 3, and 5, and thus, were designated as 1Ets#1, 3Ets#1, and 5Ets#1, respectively. NAU751 was identified as a disomic substitution line with chromosome 3A of wheat replaced by chromosome 3Ets#1. Line NAU702 has a high level of resistance to scab and will be used in chromosomal engineering and development of improved wheat germplasm for scab resistance breeding.
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  • 86
    ISSN: 1573-5028
    Keywords: Arabidopsis ; CLAVATA1 ; genome sequencing ; RFLP ; YAC contig
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract With the advance of Arabidopsis as a model system for understanding plant genetics, development and biochemistry, a detailed description of the genome is necessary. As such, focused projects are underway to map and sequence the Arabidopsis nuclear genome. We have characterized a region of chromosome 1, surrounding the CLAVATA1 (CLV1) locus. Three (RFLP) clones were mapped relative to clv1-1, and were used to construct an ca. 700 kb yeast artificial chromosome (YAC) contig. Three cosmids spanning the CLV1 locus were analyzed and ca. 24 kb of genomic DNA was sequenced, including a continuous stretch of 18 kb. In addition to generating clones in this region of chromosome 1, we have analyzed the size, spacing and organization of several contiguous genes.
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  • 87
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    Plant and soil 209 (1999), S. 233-243 
    ISSN: 1573-5036
    Keywords: bioassay ; carbon ; erosion ; forest soil ; nitrogen ; wildfire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A ponderosa pine/Douglas-fir forest (Pinus ponderosa Dougl., Pseudotsuga menziesii (Mirb.) Franco; PP/DF) and a lodgepole pine/Engelmann spruce forest (Pinus contorta Loud., Picea engelmannii Parry ex Engelm.; LP/ES) located on the eastern slopes of the Cascade Mountains in Washington state, USA, were examined following severe wildfire to compare total soil carbon and nitrogen capitals with unburned (control) forests. One year after fire, the average C content (60 cm depth) of PP/DF and LP/ES soil was 30% (25 Mg ha-1) and 10% (7 Mg ha-1) lower than control soil. Average N content on the burned PP/DF and LP/ES plots was 46% (3.0 Mg ha-1) and 13% (0.4 Mg ha-1) lower than control soil. The reduction in C and N in the PP/DF soil was largely the result of lower nutrient capitals in the burned Bw horizons (12–60 cm depth) relative to control plots. It is unlikely that the 1994 fire substantially affected nutrient capitals in the Bw horizons; however, natural variability or past fire history could be responsible for the varied nutrient capitals observed in the subsurface soils. Surface erosion (sheet plus rill) removed between 15 and 18 Mg ha-1 of soil from the burned plots. Nutrient losses through surface erosion were 280 kg C ha-1 and 14 kg N ha-1 in the PP/DF, whereas LP/ES losses were 640 and 22 kg ha-1 for C and N, respectively. In both forests, surface erosion of C and N was ∼1% to 2% of the A-horizon capital of these elements in unburned soil. A bioassay (with lettuce as an indicator plant) was used to compare soils from low-, moderate- and high-severity burn areas relative to control soil. In both forests, low-severity fire increased lettuce yield by 70–100% of controls. With more severe fire, yield decreased in the LP/ES relative to the low-intensity burn soil; however, only in the high-severity treatment was yield reduced (14%) from the control. Moderate- and high-severity burn areas in the PP/DF were fertilized with ∼56 kg ha-1 of N four months prior to soil sampling. In these soils, yield was 70–80% greater than the control. These results suggest that short-term site productivity can be stimulated by low-severity fire, but unaffected or reduced by more severe fire in the types of forests studied. Post-fire fertilization with N could increase soil productivity where other environmental factors do not limit growth.
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  • 88
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    Plant and soil 212 (1999), S. 143-151 
    ISSN: 1573-5036
    Keywords: carrot ; green manure ; nitrogen ; organic production ; rooting depth ; root distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cover crops grown as green manure or for other purposes will affect nitrogen (N) distribution in the soil, and may thereby alter root growth of a succeeding crop. During two years, experiments were performed to study effects of nitrogen supply by green manure on root development of carrots (Daucus carota L). Total root intensity (roots cm−2 on minirhizotrons) was significantly affected by the green manures, and was highest in the control plots where no green manure had been grown. Spread of the root system into the interrow soil was also affected by green manure treatments, as the spread was reduced where spring topsoil Nmin was high. Although N supply and distribution in the soil profile differed strongly among the treatments, no effect was observed on the rooting depth of the carrot crops. Across all treatments the rooting front penetrated at a rate of 0.82 and 0.68 mm day−1 °C−1 beneath the crop rows and in the interrow soil, respectively. The minirhizotrons only allowed measurements down to 1 m, and the roots reached this depth before harvest. Extrapolating the linear relationship between temperature sum and rooting depth until harvest would lead to rooting depths of 1.59 and 1.18 m under the crop rows and in the interrow soil respectively. Soil analysis showed that the carrot crop was able to reduce Nmin to very low levels even in the 0.75 to 1.0 m soil layer, which is in accordance with the root measurements. Still, where well supplied, the carrots left up 90 kg N ha−1 in the soil at harvest. This seemed to be related to a limited N uptake capacity of the carrots rather than to insufficient root growth in the top metre of the soil.
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  • 89
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    Hydrobiologia 401 (1999), S. 215-227 
    ISSN: 1573-5117
    Keywords: 18S rRNA ; protistan biogeography ; protists ; RFLP ; oligonucleotide probe ; protistan community structure ; in-situ hybridization ; microbial ecology ; molecular ecology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
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  • 90
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    Hydrobiologia 410 (1999), S. 111-122 
    ISSN: 1573-5117
    Keywords: phosphorus ; nitrogen ; retention ; river systems ; specific runoff ; hydraulic load
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The total nutrient inputs (emissions) from point and diffuse sources into 100 different river basins in Europe are compared with the measured load (transport). The catchment areas range between 121 and 194 000 km2. Other characteristic parameters of the basins, including specific runoff, surface water area and the nutrient concentration show large differences. Independent of the different methods applied for estimating nutrient emissions, these are in general higher than the actual transport. The ratio of the transport to the emission was used to exclude the effects of basin size and to facilitate comparisons between river basins. A statistical model of the retention, including net sedimentation and denitrification, is derived for the description of the discrepancy between the measured transport and the estimated total emission of nutrients, which is assumed to reflect retention of nutrients in a river system. It was found that the load-weighted retention of phosphorus is controlled practically only by the specific runoff of the basin. The load- weighted retention of nitrogen is further dependent on the proportion of the basin area occupied by surface water, the basin size itself and the mean annual nitrogen concentration at a specific monitoring station. Application of the statistical model reduces the mean deviation between the calculated emissions and the values given by different authors from about 40% to 20%.
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  • 91
    ISSN: 1573-515X
    Keywords: atmospheric deposition ; moss ; bog ; nitrogen ; phosphorus ; water table
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Nitrogen additions as NH4NO3 corresponding to 0 (N0), 1 (N1), 3 (N3) and 10 (N10) g N m-2 yr-1 were made to Sphagnum magellanicum cores at two-week intervals in situ at four sites across Europe, i.e. Lakkasuo (Finland), Männikjärve (Estonia), Moidach More (UK) and Côte de Braveix (France). The same treatments were applied in a glasshouse experiment in Neuchâtel (Switzerland) in which the water table depth was artificially maintained at 7, 17 and 37 cm below the moss surface. In the field, N assimilation in excess of values in wet deposition occurred in the absence of growth, but varied widely between sites, being absent in Lakkasuo (moss N:P ratio 68) and greatest in Moidach More (N:P 21). In the glasshouse, growth was reduced by lowering the water table without any apparent effect on N assimilation. Total N content of the moss in field sites increased as the mean depth of water table increased indicating growth limitation leading to increased N concentrations which could reduce the capacity for N retention. Greater contents of NH4+ in the underlying peat at 30 cm depth, both in response to NH4NO3 addition and in the unamended cores confirmed poor retention of inorganic N by the moss at Lakkasuo. Nitrate contents in the profiles at Lakkasuo, Moidach More, and Côte de Braveix were extremely low, even in the N10 treatment, but in Männikjärve, where the mean depth of water table was greatest and retention absent, appreciable amounts of NO3- were detected in all cores. It is concluded that peatland drainage would reduce the capture of inorganic N in atmospheric deposition by Sphagnum mosses.
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  • 92
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    Hydrobiologia 393 (1999), S. 35-43 
    ISSN: 1573-5117
    Keywords: eutrophication ; modelling ; biogeochemical cycles ; nitrogen ; phosphorus ; load reduction ; Baltic Sea ; Gulf of Finland
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The entire Baltic Sea, as well as many of its different sub-regions, are subject to eutrophication due to high nutrient inputs. To plan expensive water management measures one needs a tool to quantify effects of different water management policy decisions. The tools implemented here are simulation models based on similar descriptions of biochemical interactions in the water and sediments but coupled to different hydrodynamical models. For the Baltic Proper a 1D physical model with high vertical resolution but horizontally integrated was used. Simulations for 20 years made with 50% load reduction each 5 year show that for this domain and at these scales the recovery would take decades. The most effective is reduction of phosphorus, while reduction of only nitrogen leads to a dramatic increase in cyanobacteria blooms. For the Gulf of Finland a high-resolution 3D hydrodynamic model was coupled to a more crude 3D-box biogeochemical model describing concrete conditions during August and November 1991. In the Eastern Gulf of Finland the effects of a 50% load reduction from the St. Petersburg region are pronounced even after two weeks. Here, nitrogen reduction would be more beneficial than that of phosphorus, both locally and at a larger scale. The conclusion from these simulations is that the difference in effects of nitrogen versus phosphorus reduction is dependent on scales and locations of management.
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  • 93
    ISSN: 1573-5117
    Keywords: sedimentation ; carbon ; nitrogen ; phosphorus ; resuspension ; export production ; Baltic Sea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal changes of total particulate material (TPM), particulate organic carbon (POC), nitrogen (PON) and phosphorus (PTP) concentrations in the water column, in sediment traps and on the sediment surface were studied in the SW coast of Finland, Baltic Sea, from March to November 1992. Sampling was carried out along a coastal gradient from the fjord-like, semi-enclosed Pojo Bay to the outer archipelago and open sea area. In Pojo Bay, TPM sedimentation rates were high and relatively constant, and had low organic carbon contents throughout the seasonal cycle. Resuspension was estimated to contribute 〉 90% of total sedimentation of POC and PON. Clear seasonality in sedimentation with high settling rates of primary organic material in spring, low sedimentation rates during summer and a considerable increase of resuspension during autumn was found in the outer archipelago and open sea. The C:N:P ratios of suspended, settled and sediment surface material indicated greater sedimentary loss of N (as compared to P and C) and closer coupling between pelagial and benthos in the archipelago and open sea area than in Pojo Bay. The sedimentation of P was 20–50% more effective (as compared to N and C) in Pojo Bay than elsewhere. These results indicate that the shift of planktonic nutrient limitation (from P to N limitation) is enhanced due to the more efficient sedimentation of the main limiting element along the estuarine gradient. The primary sedimentation of organic carbon (approximating export flux from the pelagic system) during the whole study period was estimated to be 30–48% of the total net primary production. This indicates that despite the differences in the salinity, nutrient dynamics and planktonic community structure along the coastal gradient, a relatively constant fraction of the annual primary production is exported from the pelagic system by sedimentation.
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  • 94
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    Hydrobiologia 395-396 (1999), S. 41-60 
    ISSN: 1573-5117
    Keywords: nitrogen ; phosphorus ; non-point source ; export ; catchment modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sustainable lake management for nutrient-enriched lakes must be underpinned by an understanding of both the functioning of the lake, and the origins of changes in nutrient loading from the catchment. To date, limnologists have tended to focus on studying the impact of nutrient enrichment on the lake biota, and the dynamics of nutrient cycling between the water column, biota and sediments within the lake. Relatively less attention has been paid to understanding the specific origins of nutrient loading from the catchment and nutrient transport pathways linking the lake to its catchment. As such, when devising catchment management strategies to reduce nutrient loading on enriched lakes, assumptions have been made regarding the relative significance of non-point versus point sources in the catchment. These are not always supported by research conducted on catchment nutrient dynamics in other fields of freshwater science. Studies on nutrient enrichment in lakes need to take account of the history of catchment use and management specific to each lake in order to devise targeted and sustainable management strategies to reduce nutrient loading to enriched lakes. Here a modelling approach which allows quantification of the relative contribution of nutrients from each specific point and non-point catchment source over the course of catchment history is presented. The approach has been applied to three contrasting catchments in the U.K. for the period 1931 to present. These are the catchment of Slapton Ley in south Devon, the River Esk in Cumbria and the Deben Estuary in Suffolk. Each catchment showed marked variations in the nature and intensity of land use and management. The model output quantifies the relative importance of point source versus non-point livestock and land use sources in each of the catchments, and demonstrates the necessity for an understanding of site-specific catchment history in devising suitable management strategies for the reduction of nutrient loading on enriched lakes.
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  • 95
    ISSN: 1573-5117
    Keywords: nitrogen ; Gracilaria gracilis ; cultivation ; stable isotopes ; δ15N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Small Bay, Saldanha, the water becomes highly stratified in summer. The cold bottom layer (of upwelling origin) is rich in nitrogen, some of which enters the surface layer by advection. However, the surface water often becomes warm and oligotrophic leading to poor growth or death of Gracilaria gracilis grown in experimental suspended systems. At the same time, large quantities of nitrogen-rich fish waste are released at a particular site in the bay. We tested the hypothesis that Gracilaria grown close to the site of waste release (1.5 km away and in the waste plume) would grow faster than at the control site 3.5 km away. In October and November (early summer) 1996, all the Gracilaria at the control site died, while growth at the fish waste site was good (between 8 and 10% day−2). In November–December control plants grew slightly faster than those from the waste site, in February the reverse occurred, and subsequently (March–June) growth was s imilar at both sites as winter winds caused mixing of the water column. These results, and analyses of the C/N ratios of the Gracilaria tissues provide some support for our hypothesis. Also, analyses of the stable N isotope ratios in the Gracilaria tissues indicate that there is considerable uptake of the fish-waste N even at the control site. We conclude that while proximity to the waste site may sometimes benefit the Gracilaria, the fish waste would in fact provide a significant source of N for seaweed cultivated throughout the northern area of Small Bay, particularly when the water is highly stratified in summer.
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  • 96
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    Hydrobiologia 408-409 (1999), S. 389-394 
    ISSN: 1573-5117
    Keywords: mictic type ; water transparency ; nitrogen ; phosphorus ; chlorophyll:nutrient ratio ; chlorophyll:seston ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Data for comparison are from 17 dimictic and four polymictic lakes interconnected to form a system of the Great Masurian Lakes. Both summer epilimnetic total phosphorus and chlorophyll were higher in dimictic than in polymictic lakes. Chlorophyll was probably not limited either by phosphorus or by nitrogen in shallow lakes. Utilization of phosphorus in terms of chlorophyll:particulate phosphorus and chlorophyll:particulate nitrogen ratios was similar in the two groups of lakes. Significant differences were found, however, in the chlorophyll:seston ratio, higher in dimictic lakes. These observations together suggest that seston in shallow lakes contains a significant, though unpredictable contribution of detritus/mineral particles much poorer in phosphorus than those in dimictic lakes. Secchi disc depth was better explained in shallow lakes by seston variability than by chlorophyll. Thus, algal production in shallow masurian lakes seems to be limited by light conditions resulting from resuspension of non-living particles while the production in deep lakes is nutrient (both nitrogen and phosphorus) limited.
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  • 97
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    Hydrobiologia 408-409 (1999), S. 359-365 
    ISSN: 1573-5117
    Keywords: eutrophication ; trends ; lakes ; phosphorus ; nitrogen ; chlorophyll-a ; transparency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relation between (inter)national programs aiming at nutrient load reduction and changes in eutrophication has been studied for 231 Dutch lakes over the period 1980–1996. Trends in total-phosphorus (P) and total-nitrogen (N) were negative, as determined by analysis of both individual lakes and the complete data set. The relative trends in the nutrient concentrations as well as in the N/P ratio correspond with the significantly reduced P emission and the limited reduction of N emission in The Netherlands since the beginning of the 1980s. Negative trends in chlorophyll-aand positive trends in Secchi-disc transparency may be partly explained by reduced nutrient concentrations. Perspectives for the nearby future are discussed. Lake characteristics had only a minor impact on the trends. The improvement of the water quality was found for all subsets of average depth, surface area, hydraulic retention time and soil type. Furthermore, the effect of restoration measures and meteorological conditions on the trends were studied. Biomanipulation resulted in an additional improvement of several water quality variables compared to lakes that were only subject to (inter)national programs on nutrient load reduction. Specific measures resulting in additional P load reduction resulted only in lowered P concentrations. Severe winters resulted in lower chlorophyll-aconcentrations in the following summer and dry conditions in spring were favourable for all eutrophication variables in the following summer.
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  • 98
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    Hydrobiologia 410 (1999), S. 87-96 
    ISSN: 1573-5117
    Keywords: eutrophication ; nutrient limitation ; nitrogen ; phosphorous ; silicate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nutrient loading by riverine input into estuarine systems has increased by 6–50 times for the N load from pristine conditions to present, whereas a 18–180 times increase has been observed in the P load. Reductions in the ratio of N to P delivery has also occurred with time. In a review of nutrient limitation in estuarine systems, it is shown that many estuarine systems display P limitation in the spring, switching to N limitation in the summer with some estuaries displaying dissolved silicate limitation of the spring diatom bloom. Historical and recent changes in nutrient loading and their effect on nutrient limitation have intensified the debate on the control of nutrient delivery to estuaries from both agricultural and point sources, and as to what nutrient (N or P) should be managed for in estuarine systems. It is hypothesized that potential reductions in P may help oxygen depletion especially in deep estuaries and reduce fast growing macrophytes such as Ulva sp., although P reductions probably will have little effect on summer chlorophyll concentrations, an important recreational management goal. Reductions in N loading should reduce summer chlorophyll concentrations and improve the conditions for submerged aquatic vegetation and thus improve ecosystem functioning. Finally, if only P reductions are pursued, that is if we are able to reduce P such that it is limiting year around in estuarine systems, it is likely that the export of N from estuarine systems would increase to the bordering N-limited marine systems, thus only exporting the problem of enhanced production with eutrophication.
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  • 99
    ISSN: 1573-515X
    Keywords: Chihuahuan desert ; desert ; desertification ; grassland ; nitrogen ; nutrient budgets ; phosphorus ; runoff
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Rainfall simulation experiments were performed in areas of semiarid grassland (Bouteloua eriopoda) and arid shrubland (Larrea tridentata) in the Chihuahuan desert of New Mexico. The objective was to compare the runoff of nitrogen (N) and phosphorus (P) from these habitats to assess whether losses of soil nutrients are associated with the invasion of grasslands by shrubs. Runoff losses from grass- and shrub-dominated plots were similar, and much less than from bare plots located in the shrubland. Weighted average concentrations of total dissolved N compounds in runoff were greatest in the grassland (1.72 mg/l) and lowest in bare plots in the shrubland (0.55 mg/l). More than half of the N transported in runoff was carried in dissolved organic compounds. In grassland and shrub plots, the total N loss was highly correlated to the total volume of discharge. We estimate that the total annual loss of N in runoff is 0.25 kg/ha/yr in grasslands and 0.43 kg/ha/yr in shrublands – consistent with the depletion of soil N during desertification of these habitats. Losses of P from both habitats were very small.
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  • 100
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    Environmental monitoring and assessment 58 (1999), S. 173-200 
    ISSN: 1573-2959
    Keywords: Baltic Sea ; nitrogen ; phosphorous ; riverine load ; timeseries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This article presents the results of the first critical examination of time series of riverine nutrient-load data for the entire Baltic Sea drainage area. Water quality data collected by or for the different national environmental agencies were compiled and analysed statistically to identify and remove inconsistent or obviously incorrect observations. Moreover, sampling tours were undertaken to acquire additional information about the present nutrient concentrations in the largest rivers in the study area. Gaps in the time series of approved data were then filled in by employing statistical interpolation and extrapolation methods. Thereafter, the concentration and runoff data were combined to obtain estimates of monthly nutrient loads for the time period 1970–93. The results of the calculations showed that although there had been substantial changes in land use, atmospheric deposition and wastewater treatment in many parts of the study area, the total riverine loads of nitrogen (N) and phosphorus (P) to the Baltic Sea have been fairly constant since 1980, and most likely also since 1970. Moreover, the interannual variation was clearly correlated to the runoff. The mean annual loads for the time period 1980–93 were found to be about 825 000 tonnes N and 41 000 tonnes P, respectively. This implies that (i) several other investigators have strongly underestimated the riverine loads of nutrients, especially the nitrogen, and that (ii) the riverine loads by far exceed the input to the Baltic Sea from other sources, {i.e.} atmospheric deposition, direct emissions from cities and industries along the Baltic Sea coast and nitrogen fixation by marine algae.
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