| 1. |
- Ek, Hans, et al.
(författare)
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Carbon and nitrogen flow in Silver birch and Norway spruce connected by a common mycorrhizal mycelium
- 1996
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 6:6, s. 465-467
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Tidskriftsartikel (refereegranskat)abstract
- Spruce and birch seedlings were grown together in boxes filled with unsterile pear. Both seedlings were colonized by the ectomycorrhizal fungus Scleroderma citrinum. The two plants thus shared a common external mycelium. N-15-labelled ammonium was supplied exclusively to the fungus, while the birch or the spruce plant was continuously fed with C-13-labelled CO2 for 72 h. The carbon and nitrogen transfer rates were strikingly different for birch and spruce seedlings. The mycorrhizal mycelium received carbohydrates mainly from the birch plant and the nitrogen transfer by the fungus to the plants was largely directed towards the birch. Carbon assimilates were also transferred in both directions between birch and spruce; however, there was no conclusive evidence for a net transfer of carbon between the plants.
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| 2. |
- Timonen, Sari, et al.
(författare)
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Dynamics of cytoskeletal proteins in developing pine ectomycorrhiza
- 1996
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 6:5, s. 423-429
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Tidskriftsartikel (refereegranskat)abstract
- Mycorrhizal short roots of Pinus contorta Dougl. ex Loud colonized by Suillus variegatus (Sow. ex Fr.) O. Kuntze or Paxillus involutus (Batsch) Fr. were collected 1->60 days after fungal contact. The proteins of the inoculated roots were extracted, electrophoretically separated, blotted and immunostained for alpha-tubulin and actin. The development of the mycorrhiza was also followed microscopically. The signal of plant alpha-tubulin was stronger than the signal of fungal alpha-tubulin during the first 5 days in S. variegatus mycorrhiza and was then exceeded by fungal alpha-tubulin. This correlated well with the increase of fungal mycelium in the mycorrhiza. A transient drop in both plant and fungal alpha-tubulin signals was observed 20 days after fungal contact, suggesting a change in the metabolism of the mycorrhiza. The signals for plant and fungal actins in the mycorrhiza increased steadily during early infection and then remained at a high level as the mycorrhiza matured. Similar trends were observed in P. contorta-P. involutus mycorrhiza. The data from P. contorta-S. variegatus mycorrhizas suggests that alpha-tubulin is a growth-related protein, subject to changes, while the amount of actin reflects the general metabolic activity of the mycorrhiza. In both mycorrhizal systems clear alpha-tubulin and actin signals were detected 60 days after colonization, which indicates that the mycorrhizas were metabolically active in spite of their withered appearance.
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| 3. |
- Wallander, Håkan, et al.
(författare)
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Relationships between fungal uptake of ammonium, fungal growth and nitrogen availability in ectomycorrhizal Pinus sylvestris seedlings
- 1999
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Ingår i: Mycorrhiza. - : Springer Science and Business Media LLC. - 1432-1890 .- 0940-6360. ; 8:4, s. 215-223
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen deposition and intentional forest fertilisation with nitrogen are known to affect the species composition of ectomycorrhizal fungal communities. To learn more about the mechanisms responsible for these effects, the relations between fungal growth, nitrogen uptake and nitrogen availability were studied in ectomycorrhizal fungi in axenic cultures and in symbiosis with pine seedlings. Effects of different levels of inorganic nitrogen (NH4) on the mycelial growth of four isolates of Paxillus involutus and two isolates of Suillus bovinus were assessed. With pine seedlings, fungal uptake of N-15-labelled NH4 was studied in shortterm incubation experiments (72 h) in microcosms and in long-term incubation experiments (3 months) in pot cultures. For P. involutus growing in symbiosis with pine seedlings, isolates with higher NH4 uptake were affected more negatively at high levels of nitrogen availability than isolates with lower uptake. More NH4 was allocated to shoots of seedlings colonised by a high-uptake isolate, indicating transfer of a larger fraction of assimilated NH4 to the host than with isolates showing lower NH4 uptake rates. Thus low rates of N uptake and N transfer to the host may enable EM fungi avoid stress induced by elevated levels of nitrogen. Seedlings colonised by S. bovinus transferred a larger fraction of the N-15 label to the shoots than seedlings colonised by P. involutus. Seedling shoot growth probably constituted a greater carbon sink in pot cultures than in microcosms, since the mycelial growth of P. involutus was more sensitive to high NH4 in pots. There was no homology in mycelial growth rate between pare culture and growth in symbiosis, but N uptake in pure culture corresponded to that during growth in symbiosis. No relationship was found between deposition of antropogenic nitrogen at the sites of origin of the P. involutus isolates and their mycelial growth or uptake of inorganic nitrogen
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