| 1. |
- Andersson, Solbritt, et al.
(författare)
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Effects of liming on the uptake of organic and inorganic nitrogen by mycorrhizal (Paxillus involutus) and non-mycorrhizal Pinus sylvestris plants
- 1997
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 135:4, s. 763-771
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Tidskriftsartikel (refereegranskat)abstract
- Seedlings of Pinus sylvestris L. were grown in Plexiglas(R) observation chambers in limed (CaCO3, pH 5.0 and 5.9) and untreated (pH 4.1) peat. The seedlings were either colonized by the mycorrhizal fungus Paxillus involutus (Batsch: Fr.) Fr. Or were non-mycorrhizal. After 18 wk in the observation chambers, N-15-labelled organic nitrogen, as lyophilized and ground mycelium of Suillus variegatus (Swartz: Fr.) O. Kuntze, or ammonium, was added to the peat. The plants were harvested after an uptake period of 14 d. Irrespective of the nitrogen form added, liming decreased both the content and concentration of N-15 in nonmycorrhizal plants, and, to a lesser extent, those in mycorrhizal plants. In mycorrhizal plants the uptake of N-15 was not correlated with area colonized by the mycorrhizal mycelium. The amount of KCl-extractable N-15 in peat without plants and mycorrhizal fungi decreased with liming. It is proposed that liming induced chemical or microbial immobilization of the added N-15. This is suggested to be the main reason for the decreased uptake of N-15 in lime treatments.
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| 2. |
- 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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| 3. |
- Ek, H., et al.
(författare)
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Growth and assimilation of NH4+ and NO3- by Paxillus involutus in association with Betula pendula and Picea abies as affected by substrate pH
- 1994
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 128:4, s. 629-637
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Tidskriftsartikel (refereegranskat)abstract
- The influence of pH on the growth and assimilation of N-15-labelled ammonium and nitrate was studied in intact ectomycorrhizal systems consisting of Betula pendula Roth and Picea abies (L.) Karst. colonized with a common mycelium of Paxillus involutus (Batsch) Fr. The plants were grown together in Plexiglass observation chambers containing non-sterile peat with three different pH values, 4.0, 5.1 and 6.1. The mycorrhizal mycelium was allowed to grow over a barrier into an area of peat from which plant roots were excluded. Labelled NH4NO3 was supplied, either as (NH4NO3)-N-15 or as (NH4NO3)-N-15, exclusively to the fungal mycelium. Shoots and roots were analyzed for N-15 in total nitrogen while the mycelium was analyzed for N-15 in NH4+, NO3- and free amino acids. The N-15 labelling pattern indicated that ammonium was immediately assimilated into amino acids, primarily glutamine, by the fungal mycelium at the uptake site. The amino acids were then translocated to the mycorrhizal roots. In contrast, nitrate-N was not assimilated in the mycelium but rather transferred to the mycorrhizal roots as nitrate. Mycelial uptake and transfer of N to the spruce and birch seedlings were significantly higher for NH4-N than for NO3-N. No firm conclusions about pH effects on the preferential uptake of ammonium and nitrate could be drawn. However, pH had a pronounced effect on the mycelial growth of P. involutus which was hampered severely at pH 6.1 and to a lesser extent at pH 5.1.
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| 4. |
- van Aarle, Ingrid, et al.
(författare)
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Arbuscular mycorrhizal fungi respond to the substrate pH of their extraradical mycelium by altered growth and root colonization
- 2002
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 155:1, s. 173-182
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Tidskriftsartikel (refereegranskat)abstract
- To test the response of arbuscular mycorrhizal (AM) fungi to a difference in soil pH, the extraradical mycelium of Scutellospora calospora or Glomus intraradices, in association with Plantago lanceolata, was exposed to two different pH treatments, while the root substrate pH was left unchanged. Seedlings of P. lanceolata, colonized by one or other of the fungal symbionts, and nonmycorrhizal controls, were grown in mesh bags placed in pots containing pH-buffered sand (pH around 5 or 6). The systems were harvested at approximately 2-wk intervals between 20 and 80 d. Both fungi formed more extraradical mycelium at the higher pH. Glomus intraradices formed almost no detectable extraradical mycelium at lower pH. The extraradical mycelium of S. calospora had higher acid phosphatase activity than that of G. intraradices. Total AM root colonization decreased for both fungi at the higher pH, and high pH also reduced arbuscule and vesicle formation in G. intraradices. In conclusion, soil pH influences AM root colonization as well as the growth and phosphatase activities of extraradical mycelium, although the two fungi responded differently.
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| 5. |
- van Aarle, Ingrid, et al.
(författare)
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Growth and interactions of arbuscular mycorrhizal fungi in soils from limestone and acid rock habitats
- 2003
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Ingår i: Soil Biology & Biochemistry. - 0038-0717. ; 35:12, s. 1557-1564
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Tidskriftsartikel (refereegranskat)abstract
- Arbuscular mycorrhizal (AM) development in different soil types, and the influence of AM fungal hyphae on their original soil were investigated. Plantago lanceolata, which can grow in soils of a very wide pH range, was grown in two closely related limestone soils and an acid soil from rock habitats. Plants were colonised by the indigenous AM fungal community. The use of compartmented systems allowed LIS to compare soil with and without mycorrhizal hyphae. Root colonisation of P. lanceolata was markedly higher in the limestone soils (30-60%) than in the acid soil (5 -20%), both in the original habitat and in the experimental study. Growth of extraradical AM fungal hyphae was detected in the limestone soils, but not in the acid soil, using the signature fatty acid 16: 1 omega5 as biomass indicator. Analysis of signature fatty acids demonstrated an increased microbial biomass in the presence of AM fungal hyphae as judged for example from ail increased amount of NLFA 16:0 with 30 nmol g(-1) in one of the limestone soils. Bacterial activity, but not soil phosphatase activity, was increased by around 25% in the presence of mycorrhizal hyphae in the first harvest of limestone soils. AM fungal hyphae can thus stimulate microorganisms. However, no effect of AM hyphae was observed on the soil pH or organic matter content in the limestone soils and the available P was not depleted. (C) 2003 Elsevier Ltd. All rights reserved.
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| 6. |
- van Aarle, Ingrid, et al.
(författare)
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Microscopic detection of phosphatase activity of saprophytic and arbuscular mycorrhizal fungi using a fluorogenic substrate
- 2001
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Ingår i: Mycologia. - 0027-5514. ; 93:1, s. 17-24
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Tidskriftsartikel (refereegranskat)abstract
- The location and activity of saprophytic and arbuscular mycorrhizal (NM) fungal phosphatases have been investigated with a fluorogenic substrate (ELF) that forms a fluorescent crystalline precipitate at the site of phosphatase activity. This ELF substrate method was compared with other detection methods such as fast blue RR salt staining and p-nitrophenyl phosphate. The ELF substrate was successfully used to determine the location of phosphatase activity in AM fungal hyphae, and to visualize the active AM fungal colonization of roots. The substrate was taken up by fungal hyphae, when acid and alkaline buffers were used, and internal phosphatase activity was visualized. The release of both acid and alkaline phosphatases by a saprophytic fungus to an agar medium was demonstrated. ELF combined with an alkaline buffer led to specific staining of active fungal structures such as hyphae, arbuscules and young vesicles in AM-colonized roots. The results indicate that the ELF substrate is a sensitive indicator for fungal phosphatase activity and that it can be used to visualize hyphal phosphatase activity in both roots and external hyphae.
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| 7. |
- Johansson, Tomas, et al.
(författare)
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Transcriptional responses of Paxillus involutus and Betula pendula during formation of ectomycorrhizal root tissue
- 2004
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Ingår i: Molecular Plant-Microbe Interactions. - 0894-0282 .- 1943-7706. ; 17:2, s. 202-215
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Tidskriftsartikel (refereegranskat)abstract
- In order to obtain information on genes specifically expressed in the ectomycorrhizal symbiosis, 3,555 expressed sequence tags (ESTs) were analyzed from a cDNA library constructed from ectomycorrhiza formed between the basidiomycete Paxillus involutus and birch (Betula pendula). cDNA libraries from saprophytically growing fungus (3,964 ESTs) and from axenic plants (2,532 ESTs) were analyzed in parallel. By clustering all the EST obtained, a nonredundant set of 2,284 unique transcripts of either fungal or plant origin were identified. The expression pattern of these genes was analyzed using cDNA microarrays. The analyses showed that the plant and fungus responded to the symbiosis by altering the expression levels of a number of enzymes involved in carbon metabolism. Several plant transcripts with sequence similarities to genes encoding enzymes in the tricarboxylic cycle and electron transport chain were down regulated as compared with the levels in free-living roots. In the fungal partner, a number of genes encoding enzymes in the lipid and secondary metabolism were down regulated in mycorrhiza as compared with the saprophytically growing mycelium. A substantial number of the ESTs analyzed displayed significant sequence similarities to proteins involved in biotic stress responses, but only a few of them showed differential expression in the mycorrhizal tissue, including plant and fungal metallothioneins and a plant defensin homologue. Several of the genes that were differentially expressed in the mycorrhizal root tissue displayed sequence similarity to genes that are known to regulate growth and development of plant roots and fungal hyphae, including transcription factors and Rho-like GTPases.
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| 8. |
- Andersson, Solbritt, et al.
(författare)
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Effects of lime (CaCO3) on ectomycorrhizal colonization of Picea abies (L.) Karst. - seedlings planted in a spruce forest
- 1995
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 10:2, s. 149-154
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Tidskriftsartikel (refereegranskat)abstract
- In two consecutive years, seedlings of Norway spruce (Picea abies) were planted in a 50-yr-old Norway spruce forest in limed (3.8 tons CaCO3 ha-1) and control plots. After 6 months they were harvested and the mycorrhizal status of the roots was analysed. Six types of mycorrhiza were distinguished. Three decreased after liming, two increased and one was not affected consistently by the liming. The effects on the total mycorrhizal colonization of the roots were opposite for the two years, indicating that the effects of liming are influenced strongly by other environmental factors. Statistical analysis also revealed pronounced natural variation in space. An inventory of the sporocarp-producing fungi showed that the number of saprotrophic species producing sporocarps was significantly higher in the limed plots whereas the number of ectomycorrhizal species was lower in the limed plots, compared with the control plots. It is concluded that more information is needed concerning the effects of liming on different soil types before any general conclusions can be made about its effects on mycorrhizal colonization.
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| 9. |
- Arnebrant, Kristina, et al.
(författare)
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Changes in microfungal community structure after fertilization of Scots pine forest soil with ammonium-nitrate or urea
- 1990
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 22:3, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- The microfungal population structure of two Scots pine forest soils in Southern Sweden was studied 8–13 yr after nitrogen fertilization. The different fertilizers used. ammonium nitrate and urea. influenced the species composition in different ways. The main effect of the NH4NO3 treatment was an increased isolation frequency of Penicillium spinulosum and 4Oidiodendron echinulatum, while Penicillium cf. brevi-compactum. Mortierella subgenus Mortierella. Chaunopycnis alba and Oidiodendron griseum were isolated less frequently in ammonium nitrate-amended treatments compared to the non-fertilized control. In the urea-fertilized plots the isolation frequency of P. cf. brevi-compactum increased, while that of C. alba. O. echinulatum, O. griseum and P. spinulosum decreased in comparison with control plots. The changes in species composition were most evident at the highest rate of application, 600 kg N ha−1, especially when NH4NO3 was used as a fertilizer.
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| 10. |
- Arnebrant, Kristina, et al.
(författare)
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Effects of different fertilizer treatments on ectomycorrhizal colonization potential in 2 Scots pine forests in Sweden
- 1992
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Ingår i: Forest Ecology and Management. - : Elsevier BV. - 1872-7042 .- 0378-1127. ; 53:1-4, s. 77-89
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Tidskriftsartikel (refereegranskat)abstract
- Ectomycorrhizal fungal colonization potential was studied in two low-productivity Scots pine (Pinus sylvestris L.) forests in Sweden treated with different fertilizers. Young Pinus sylvestris seedlings were used as baits for ectomycorrhizal fungi for one growing season and the total ectomycorrhizal colonization level and frequencies of different types were recorded. One of the experimental sites had been fertilized once with 600 kg nitrogen (N) ha-1, either as ammonium nitrate or urea, 13 years previously. At this site no difference in the total number of ectomycorrhizal root tips was found between the different treatments and approximately 70% of all root tips were ectomycorrhizal. The other experimental site had been continuously fertilized for 15 years with a balanced nutrient mixture, applied either daily as a solution (IF treatment), or as solid fertilizers once a year (F treatment). The IF treatment had received 1700 kg N ha-1 and the F treatment 950 kg N ha-1 until our study was conducted. At this site a significant decrease in total ectomycorrhizal infection level was found as an effect of the fertilizer treatment. In the non-fertilized plots, 70% of all root tips were ectomycorrhizal and the corresponding figure for fertilized plots was 55%. At both sites the frequency of one of the eight classified ectomycorrhizal types decreased significantly in all fertilized plots except in the urea treatment.
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