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  • 1
    Electronic Resource
    Electronic Resource
    Hyphal transport by a vesicular-arbuscular mycorrhizal fungus of N applied to the soil as ammonium or nitrate (1993)
    Springer
    Biology and fertility of soils 16 (1993), S. 66-70 
    Details
    ISSN: 1432-0789
    Keywords: VA mycorrhiza ; Glomus intraradices ; Hyphal N transport ; Cucumis sativus ; 15N recovery ; Root compartment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Transport of N by hyphae of a vesicular-arbuscular mycorrhizal fungus was studied under controlled experimental conditions. The N source was applied to the soil as 15NH inf4 sup+ or 15NO inf3 sup- . Cucumis sativus was grown for 25 days, either alone or in symbiosis with Glomus intraradices, in containers with a hyphal compartment separated from the root compartment by a fine nylon mesh. Mineral N was then applied to the hyphal compartment as 15NH inf4 sup+ or 15NO inf3 sup- at 5 cm distance from the root compartment. Soil samples were taken from the hyphal compartment at 1, 3 and 5 cm distance from the root compartment at 7 and 12 days after labelling, and the concentration of mineral N in the samples was measured from 2 M KCl extracts. Mycorrhizal colonization did not affect plant dry weight. The recovery of 15N in mycorrhizal plants was 38 or 40%, respectively, when 15NH inf4 sup+ or 15NO inf3 sup- was applied. The corresponding values for non-mycorrhizal plants were 7 and 16%. The higher 15N recovery observed in mycorrhizal plants than in non-mycorrhizal plants suggests that hyphal transport of N from the applied 15N sources towards the host plant had occurred. The concentration of mineral N in the soil of hyphal compartments was considerably less in mycorrhizal treatments than in controls, indicating that the hyphae were able to deplete the soil for mineral N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336518
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  • 2
    Electronic Resource
    Electronic Resource
    Hyphal N transport by a vesicular-arbuscular mycorrhizal fungus associated with cucumber grown at three nitrogen levels (1994)
    Springer
    Plant and soil 160 (1994), S. 1-9 
    Details
    ISSN: 1573-5036
    Keywords: 15N ; Cucumis sativus ; Glomus intraradices ; hyphal N transport ; plant N status ; VA mycorrhiza
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cucumis sativus L. cv. Aminex (F1 hybrid) was grown alone or in symbiosis with Glomus intraradices Schenck and Smith in containers with two hyphal compartments (HCA and HCB) on either side of a root compartment (RC) separated by fine nylon mesh. Plants received a total of either 100, 200 or 400 mg N which were applied gradually to the RC during the experiment. 15N was supplied to HCA 42 d after plating, at 50 mg 15NH4 +-N kg−1 soil. Lateral movement of the applied 15N towards the roots was minimized by using a nitrification inhibitor and a hyphal buffer compartment. Non-mycorrhizal controls contained only traces of 15N after a 27 d labelling period irrespective of the amount of N supplied to the RC. In contrast, 49, 48 and 27% of the applied 15N was recovered in mycorrhizal plants supplied with 100, 200 and 400 mg N, respectively. The plant dry weight was increased by mycorrhizal colonization at all three levels of N supply, but this effect was strongest in plants of low N status. The results indicated that this increase was due partly to the improved inflow of N via the external hyphae. Root colonization by G. intraradices was unaffected by the amount of N supplied to the RC, while hyphal length increased in HCA compared to HCB. Although a considerable 15N content was detected in mycorrhizal roots adjacent to HCB, only insignificant amounts of 15N were found in the external hyphae in HCB. The external hyphae depleted the soil of inorganic N in both HCA and HCB, while the concentration of soil mineral N was still high in non-mycorrhizal containers at harvest. An exception was plants supplied with 400 mg N, where some inorganic N was present at 5 cm distance from the RC in HCA. The possibility of a regulation mechanism for hyphal transport of N is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150340
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  • 3
    Electronic Resource
    Electronic Resource
    Seasonal patterns of growth and nitrogen fixation in field-grown pea (1987)
    Springer
    Plant and soil 101 (1987), S. 29-37 
    Details
    ISSN: 1573-5036
    Keywords: assimilate partitioning ; growth analysis ; leaf area ; nitrate ; nitrogen fixation ; 15N isotope dilution ; pea ; Pisum sativum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The seasonal patterns of growth and symbiotic N2 fixation under field conditions were studied by growth analysis and use of15N-labelled fertilizer in a determinate pea cultivar (Pisum sativum L.) grown for harvest at the dry seed stage. The patterns of fertilizer N-uptake were almost identical in pea and barley (the non-fixing reference crop), but more fertilizer-N was recovered in barley than in pea. The estimated rate of N2 fixation in pea gradually increased during the pre-flowering and flowering growth stages and reached a maximum of 10 kg N fixed per ha per day nine to ten weeks after seedling emergence. This was the time of early pod-development (flat pod growth stage) and also the time for maximum crop growth rate and maximum green leaf area index. A steep drop in N2 fixation rate occurred during the following week. This drop was simultaneous with lodging of the crop, pod-filling (round pod growth stage) and the initiation of mobilization of nitrogen from vegetative organs. The application of fertilizer-N inhibited the rate of N2 fixation only during that period of growth, when the main part of fertilizer-N was taken up and shortly after. Total accumulation of fixed nitrogen was estimated to be 244, 238 and 213 kg N ha−1 in pea supplied with nil, 25 or 50 kg NO 3 − −N ha−1, respectively. About one-fourth of total N2 fixation was carried out during preflowering, one fourth during the two weeks of flowering and the remainder during post-flowering. About 55% of the amount of N present in pods at maturity was estimated to be derived from mobilization of N from vegetative organs. “Starter” N (25 or 50 kg NO 3 − −N ha−1) did not significantly influence either dry matter and nitrogen accumulation or the development of leaf area. Neither root length and root biomass determined 8 weeks after seedling emergence nor the yield of seed dry matter and nitrogen at maturity were influenced by fertilizer application.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02371027
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  • 4
    Electronic Resource
    Electronic Resource
    Symbiotic N2-fixation by the cover crop Pueraria phaseoloides as influenced by litter mineralization (1995)
    Springer
    Plant and soil 177 (1995), S. 1-10 
    Details
    ISSN: 1573-5036
    Keywords: cross-labeling ; litter mineralization ; 15N isotope dilution ; Pueraria phaseoloides ; symbiotic N2-fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The perennial legume Pueraria phaseoloides is widely used as a cover crop in rubber and oil palm plantations. However, very little knowledge exists on the effect of litter mineralization from P. phaseoloides on its symbiotic N2-fixation. The contribution from symbiotic N2-fixation (Ndfa) and litter N (Ndfl) to total plant N in P. phaseoloides was determined in a pot experiment using a 15N cross-labeling technique. For determination of N2-fixation the non-fixing plant Axonopus compressus was used as a reference. The experiment was carried out in a growth chamber during 9 weeks with a sandy soil and 4 rates of ground litter (C/N=16,2.8% N). P. phaseoloides plants supplied with the highest amount of litter produced 26% more dry matter and fixed 23% more N than plants grown in soil with no litter application, but the percentage of Ndfa decreased slightly, but significantly, from 87 to 84%. The litter N uptake was directly proportional to the rate of application and constituted 10% of total plant N at the highest application rate. Additionally, a positive correlation was found between litter N uptake and the amount of fixed N2. The total recovery of litter N in plants averaged 26% at harvest (shoot + root) and was not affected by the quantity added. A parallel incubation experiment also showed that, as an average of all litter levels, 26% of the litter N was present in the inorganic N pool. The amounts of fertilizer and soil N taken up by plants decreased with litter application, probably due to microbial immobilization and denitrification. It is concluded that, within the litter levels studied, litter mineralization will result in a higher amount of N2-fixed by P. phaseoloides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010332
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