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- Arnebrant, Kristina
(författare)
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Nitrogen amendments reduce the growth of extramatrical ectomycorrhizal mycelium
- 1994
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Ingår i: Mycorrhiza. - 1432-1890. ; 5:1, s. 7-15
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Tidskriftsartikel (refereegranskat)abstract
- The effect of three different nitrogen sources on the growth of external ectomycorrhizal mycelium was studied in Perspex micorocosms. Nonsterile peat was used as substrate. Five different fungal isolates growing in symbiosis with pine seedlings were investigated: two isolates of Paxillus involutus, one of Suillus bovinus and two unidentified ectomycorrhizal fungi isolated from ectomycorrhizal root tips. Three different nitrogen sources were used: ammonium as (NH4)2SO4, nitrate as NaNO3 and a complete nutrient solution (Ingestad 1979), and three different nitrogen concentrations, 1, 2 or 4 mg N/g dry wt. of peat. The mycelial growth of all fungi was found to be negatively affected by the nitrogen amendments, although the sensitivity to nitrogen varied between the isolates. One of the unidentified isolates was extremely sensitive and growth was completely inhibited by all nitrogen treatments. In contrast, the growth of one of the P. involutus isolates was only slightly reduced by the nitrogen amendments. The different nitrogen sources all reduced growth, and since no significant difference was found between the nitrogen sources or between the different nitrogen concentrations the results were pooled to give one value that summarized the effect of nitrogen on mycelial growth. Thus, the mycelial growth of one of the two P. involutus isolates was reduced to approximately 80% of the growth in the control, the other P. involutus and one of the unidentified fungi, vgk 2 89.10, were reduced to 40–50% of the control growth, S. bovinus to 30% of the control and the most sensitive fungus, the unidentified isolate vg 1 87.10, was reduced to 3% of the growth in the control treatment. In all experiments, the shoot to root ratio generally increased, mainly as a result of increased shoot growth.
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| 3. |
- Sundblad, K., et al.
(författare)
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Source of metals and age constraints for epigenetic gold deposits in the Skellefte and Pohjanmaa districts, central part of the Fennoscandian Shield
- 1993
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Ingår i: Mineralium Deposita. - 0026-4598 .- 1432-1866. ; 28:3, s. 181-190
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Tidskriftsartikel (refereegranskat)abstract
- The lead isotopic compositions of galena in Early Proterozoic gold deposits have been determined for three districts in northern Sweden and central Finland. The deposits are hosted by a variety of 1870-1890 Ma Svecofennian host rocks including the volcanosedimentary succession within the Skellefte District island arc in Sweden as well as I-type tonalites at Jörn (Sweden) and Pohjanmaa (Finland). The deposits are epigenetic in relation to these Svecofennian rocks and are part of a goldbearing metallogenetic belt, which can be followed for 600 km parallel to the southwestern margin of the Archaean Domain. In spite of these epigenetic relationships, the lead isotopic data indicate that the deposits are not dramatically younger than the 1870-1890 Ma Svecofennian host rocks (probably not exceeding 10-20 million years). Two principal lead sources were activated when the gold deposits were formed. The most significant source is represented by the I-type tonalites, which constitute a relatively primitive ( = 9.3) and widely distributed source in the entire metallogenic belt. In addition, the volcanic components in the westernmost part of the Skellefte District constitute an extremely primitive ( <9.0) source, which only locally was an important contributor to the epigenetic deposits in this metallogenetic belt. The significantly different lead isotopic composition estimated for these sources indicates that the volcanic rocks in the western part of the Skellefte District were not comagmatic with the I-type tonalites recognized at Jörn and central Finland.
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