| 1. |
- Cornefjord, Måns, et al.
(författare)
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A systematic review of differences in outcome between one and two stage palate repair in cleft lip and palate
- 2023
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Ingår i: Journal of Plastic Surgery and Hand Surgery. - 2000-656X. ; 58, s. 132-141
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Forskningsöversikt (refereegranskat)abstract
- The aim of this systematic review was to determine whether one-stage palatoplasty for children born with cleft lip and palate shows overall advantages in outcome compared with two-stage palatoplasty. The included studies were controlled studies of syndromic and non-syndromic children born with unilateral cleft lip and palate, bilateral cleft lip and palate, or isolated cleft palate. The interventions studied were one-stage palatoplasty and two-stage palatoplasty starting with the soft palate. The outcomes were facial growth, speech, hearing, presence of fistulae, other complications related to surgery, health-related quality of life, and health economics. In total, 14 original studies were included. Results were dichotomized into showing advantage for one- or two-stage palatoplasty for the respective outcome and compared with the results from six included systematic reviews. No overall advantage for either surgical strategy was found for any of the outcome measures. The certainty of evidence was highest for the presence of fistulae, followed by facial growth and speech. For several outcomes, the quality of the existing evidence was too low to allow for any conclusions to be drawn. Neither one- nor two-stage palatoplasty showed significant advantages in clinical outcomes compared with the other. Other aspects such as ethics, economics, or surgeon's preference might hence be of more importance. Homogenous choices of outcome measures and defined minimal clinically important differences would facilitate further research.
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| 2. |
- Voog, Hanna, et al.
(författare)
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Tillgänglighet, närhet och synlighet – gemensamma utmaningar för LUB-nätverket för att möta forskares behov av stöd vid Lunds universitet
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents a project at Lund University Libraries (LUB) during the fall of 2012, with the object to identify areas where the present research support services ought to be developed and strengthened. The project is three folded and contains a) a literature review focusing on definitions and examples of research support services as well as researchers’ needs and experiences of support services, b) a survey to get an overview of the support services offered today at LUB, the decentralized library network at Lund University, and c) focus group interviews with researchers, one group from each partaking faculty, to investigate key obstacles in their research processes. In all three parts a model of the research process schematically divided into four phases was applied; to start a project, to collect material, to process/analyze/write and to communicate the results. The first two stages of the project, the literature overview and the survey, form a background and both show that many support services are concentrated around the phases to collect material and to communicate results. The findings from the focus group interviews point to common needs and issues as well as special needs and issues related to different ways of doing and communicating research. Common for most researchers is limited time, a need for funding and an everyday fragmentation. They talk about the importance of networks, their efforts to navigate in an abundance of material and ways to find it and a need for overviews and help to understand new ways and demands to communicate. Most concern is expressed in the phases to start a project, to collect material and to communicate results. A major conclusion is that the research support services need to be available, visible and in close proximity to the researchers. Further, the development of support services needs to take into consideration both common traits as well as local variations in research practices. Therefore, discussions concerning LUB as a whole, need to be related to discussions at the single faculty libraries. Apart from knowledge about how to address the research support services at LUB, the project generates a model for how librarians can understand the research community that they are working with and with whom to create networks and partnerships for the future.
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| 3. |
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| 4. |
- 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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| 5. |
- Arnebrant, Kristina, et al.
(författare)
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Copper Tolerance of Microfungi Isolated from Polluted and Unpolluted Forest Soil
- 1987
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Ingår i: Mycologia. - : Informa UK Limited. - 0027-5514. ; 79:6, s. 890-895
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Tidskriftsartikel (refereegranskat)abstract
- Microfungi were isolated from unpolluted and copper polluted forest soils and their tolerance was tested on agar plates. Species from polluted sites were usually tolerant to Cu. The species were Paecilomyces farinosus, Beauveria bassiana, Verticillium spp. and Penicillium pactum. Sensitive species were found among Mortierella, Oidiodendron and Penicillium. usually rare in polluted sites. Little evidence for adaptation to Cu was found among isolates with short or long history of pollution.
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| 6. |
- 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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| 7. |
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| 8. |
- Arnebrant, Kristina, et al.
(författare)
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Measurements of ATP in forest humus
- 1991
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Ingår i: Soil Biology & Biochemistry. - 0038-0717. ; 23:6, s. 501-506
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of ATP as an estimate of microbial biomass C in humus was studied. Three different acid extractants, H2SO4, TCA and H3PO4 were compared, as well as two different buffers, Tris and arsenate. No difference in extraction efficiency was found when the light output was converted to ATP content using internal ATP standards, but the different extraction agents and buffers influenced the light output. Several pretreatments and storage conditions were investigated. Incubation at 25°C for 1–7 days gave ca 50% higher ATP values than incubation at 4°C. Sieving did not affect the result. For long-term storage of humus, 4°C is recommended instead of freezing, since freezing reduced the ATP content to ca 80% of the amount found in humus stored at 4°C after 2 months. Freezing of the humus extract resulted in even larger losses of ATP. Humus from eight coniferous forests in Sweden was investigated with respect to ATP content and microbial biomass, estimated with the substrate induced respiration rate method (SIR). A close linear relationship (r = 0.95) was found between the two types of measurement. Calculated from this relationship the amount of ATP (at 25°C) was 3.2μmg−1 biomass C.
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| 9. |
- 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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| 10. |
- Arnebrant, Kristina, et al.
(författare)
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Nitrogen translocation between Alnus glutinosa (L.) Gaertn. seedlings inoculated with Frankia sp and Pinus contorta Doug ex Loud seedlings connected by a common ectomycorrhizal mycelium
- 1993
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 124:2, s. 231-242
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Tidskriftsartikel (refereegranskat)abstract
- Uptake and translocation of nitrogen was studied in laboratory microcosms consisting of Alnus glutinosa (L.) Gaertn., Frankia sp., Paxillus involutus (Fr.) Fr. and Pinus contorta Dougl. ex Loud. P. involutus was shown to form a fully functional ectomycorrhizal association with alder as well as pine, and the seedlings thus became interconnected by a common mycelium. When microcosms were exposed to N-15(2) gas, interplant translocation of N-15 was observed in two out of three experiments. N-15(2) was fixed by Frankia and translocated to all other parts of the system. In the two experiments in which interplant translocation occurred, between 5 and 15 % of the N-15 recovered was found in the pine seedlings. Within seven days, fixed N2 was incorporated into amino acids in the Frankia nodules, translocated to both the A. glutinosa and P. contorta seedlings and incorporated into macromolecules. In alder seedlings, citrulline and ornithine were the free amino acids that had both the highest N-15 enrichment levels and concentrations. In pine, glutamine and citrulline had the highest N-15 concentrations, and glutamine had the highest level of N-15 enrichment. N-15 enrichment levels were greatest in the nodules, at between 5.5 and 29 % in the different amino acids and 12 % in the macromolecular fraction. Enrichment levels decreased with increasing distance from the nodules. The uptake and translocation of N-15 applied as (NH4Cl)-N-15 to the mycelium was also studied. N-15 was incorporated into amino acids in the mycelium and translocated further in this form. Generally, free amino acids had high N-15 enrichment levels in the mycelium, decreasing along the translocation pathway. Citrulline and glutamine were the amino acids with highest N-15 concentrations in all parts of the system. N-15 was also found in the macromolecular fraction.
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| 11. |
- Arnebrant, Kristina, et al.
(författare)
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Soil microbial activity in eleven Swedish coniferous forests in relation to site fertility and nitrogen fertilization
- 1996
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Ingår i: Scandinavian Journal of Forest Research. - : Informa UK Limited. - 0282-7581 .- 1651-1891. ; 11:1, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- The effect of forest fertilization on soil microbial activity and biomass was studied in 11 coniferous forests with different site fertility. Soil microbial activity was measured as respiration rate and the microbial biomass was estimated using ATP content and substrate-induced respiration rate (SIR). At all sites, except those with the highest site fertility, the microbial activity and biomass were reduced in the fertilized treatments compared with the control. The general trend indicated that the lower the site fertility, the more pronounced was the reduction of microbial biomass and activity. Some possible explanations for this effect are discussed.
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| 12. |
- Arnebrant, Kristina, et al.
(författare)
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The influence of nitrogen-fertilization on ectomycorrhizal mycelial colonization and infection
- 1990
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Ingår i: Agriculture, Ecosystems & Environment. - 1873-2305. ; 28:1-4, s. 21-25
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Tidskriftsartikel (refereegranskat)abstract
- Total ectomycorrhizal infection level and the composition of individual infection types were investigated in young Pinus sylvestris seedlings planted in a mature Scots pine forest in southern Sweden, which was N-fertilized 13 years ago. Total ectomycorrhizal infection frequency, approximately 85%, did not differ between the fertilized and non-fertilized plots, but the infection types differed between the treatments. The different fertilizers, NH4NO3 and urea, influenced the composition of ectomycorrhizal types in different ways. There were also differences in ectomycorrhiza type composition between seedlings grown in the field and seedlings grown in soil brought into the lab.
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| 13. |
- Bååth, Erland, et al.
(författare)
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Growth rate and response of bacterial communities to pH in limed and ash treated forest soils
- 1994
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Ingår i: Soil Biology & Biochemistry. - : Elsevier BV. - 0038-0717. ; 26:8, s. 995-1001
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Tidskriftsartikel (refereegranskat)abstract
- Culturable and total bacterial counts, bacterial growth rate and tolerance to pH, as well as microbial biomass, were studied in two coniferous forest soils. The pH had been changed by addition of lime and wood-ash from 4.3-4.4 to 7.0 in one soil and from 3.9-4.4 to 6.1 in the other. Higher total microbial activities and higher bacterial growth rates, measured as soil respiration rate and thymidine incorporation rate, respectively, were found in the treatments with increased pH. Similar effects of soil pH on the thymidine incorporation rate were found using two different methods, by measuring rates in either a soil slurry with all bacteria present or using a subsample of bacteria extracted from soil after homogenization-centrifugation. The number of culturable bacteria was up to 5.1 times higher in the high pH soils, while the acridine orange direct counts were unaffected by the treatments. Thus, the proportions of culturable bacteria increased in the limed and ash-treated soils compared to the untreated controls. An altered bacterial community composition due to liming was indicated by an altered response to pH, where the pH of the soil was correlated to the optimum pH for growth of the bacterial community. The ATP content of the soil was unaffected or increased in treatments with high pH compared to the control, while microbial biomass estimated by the substrate induced respiration technique (SIR) was always higher in limed and ash-treated plots.
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| 14. |
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| 15. |
- Bååth, Erland, et al.
(författare)
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Microfungi in coniferous forest soils treated with lime or wood ash
- 1993
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Ingår i: Biology and Fertility of Soils. - 0178-2762. ; 15:2, s. 91-95
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Tidskriftsartikel (refereegranskat)abstract
- Microfungal species composition was studied in coniferous forest soils which had been treated with lime or wood ash. The pH increased by about 2.5 units at the highest rate of application. Fungi were isolated 4–5 years after the treatments using a soil washing technique. At one site, Öringe, clear differences in species composition due to liming were found. Penicillium spinulosum, Oidiodendron cf. truncatum, Mortierella spp., and two sterile taxa decreased in abundance in limed areas, while Geomyces pannorum, Penicillium cf. brevicompactum, Trichoderma polysporum, and Trichosporiella sporotrichioides increased in isolation frequency. At another site, Torrmyra, the effect of liming was less pronounced, although the pH changes due to the treatments were larger compared to the Öringe site. However, T. polysporum increased, while a sterile taxon decreased in abundance in lime- and wood ash-treated plots. The changes in microfungal species composition after liming were similar to those found earlier in urea-treated soils, and opposite to those found in artifically acidified or ammonium nitrate-fertilized soils
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| 16. |
- Ek, Hans, et al.
(författare)
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Extramatrical mycelial growth, biomass allocation and nitrogen uptake in ectomycorrhizal systems in response to collembolan grazing
- 1994
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Ingår i: Applied Soil Ecology. - : Elsevier BV. - 0929-1393. ; 1:2, s. 155-169
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Tidskriftsartikel (refereegranskat)abstract
- The effects of Collembola grazing activities on the ectomycorrhizal symbiosis were studied in laboratory microcosms. Pinus contorta seedlings in association with Paxillus involutus were grown in a sandy soil and the Collembola Onychiurus armatus was added in different densities. To study effects on nutrient uptake by the extramatrical mycorrhizal mycelium, cups containing 15NH4+ and phytin amended soil were evenly distributed in the microcosms. These cups were covered with a net that allowed the mycelium to penetrate but neither Collembola nor plant roots. Extramatrical hyphal growth was impeded at a high density of O. Armatus. Low densities of O. armatus increased the extramatrical hyphal growth, the colonization rate of side plants and the biomass of P. involutus. However, the amount of P. involutus on/in the plant roots was not affected. Thus, low densities of collembolans induced a shift towards a larger proportion of P. involutus growing extramatrically. The presence of O. armatus in low numbers enhanced the uptake and transfer of 15N by P. involvus to the plants by up to 76%. The Collembola population growth was not higher in mycorrhizal compared with non-mycorrhizal microcosms while nematode population size was reduced in mycorrhizal compared with non-mycorrhizal microcosms.
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| 17. |
- 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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| 18. |
- Högberg, Mona N., et al.
(författare)
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Contrasting effects of nitrogen availability on plant carbon supply to mycorrhizal fungi and saprotrophs - a hypothesis based on field observations in boreal forest
- 2003
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Ingår i: New Phytologist. - : Wiley. - 1469-8137 .- 0028-646X. ; 160:1, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- Soil microorganisms are considered C-limited, while plant productivity is frequently N-limited. Large stores of organic C in boreal forest soils are attributed to negative effects of low temperature, soil acidity and plant residue recalcitrance upon microbial activity. We examined microbial activity, biomass and community composition along a natural 90-m-long soil N supply gradient, where plant species composition varies profoundly, forest productivity three-fold and soil pH by three units. There was, however, no significant variation in soil respiration in the field across the gradient. Neither did microbial biomass C determined by fumigation-extraction vary, while other estimates of activity and biomass showed a weak increase with increasing N supply and soil pH. Simultaneously, a phospholipid fatty acid attributed mainly to mycorrhizal fungi declined drastically, while bacterial biomass increased. We hypothesize that low N supply and plant productivity, and hence low litter C supply to saprotrophs is associated with a high plant C supply to mycorrhizal fungi, while the reverse occurs under high N supply. This should mean that effects of N availability on C supply to these functional groups of microbes acts in opposing directions.
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| 19. |
- Kytöviita, MM, et al.
(författare)
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Effects of inorganic nitrogen and phosphorus supply on nitrogen aquisition from alanine by birch seedlings in symbiosis with Paxillus involutus
- 2000
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Ingår i: Plant and Soil. - 0032-079X. ; 219:1-2, s. 243-250
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Tidskriftsartikel (refereegranskat)abstract
- Northern forests are exposed to relatively high ammonia inputs due to high atmospheric deposition and the common practise of forest fertilization. It is not known how increased soil NH4 +concentrations affect acquisition of symbiosis-mediated N from organic sources. We examined the effect of inorganic N and P availability on N acquisition from alanine by 43 weeks old birch (Betula pendula) seedlings in symbiosis with the ectomycorrhizal fungus Paxillus involutus. The seedlings were exposed for 9 weeks to nutrient additions equivalent to 43 kg N and 6.4 kg P ha-1 (low N and P availability), 250 kg N and 38 kg P ha-1(high N and P availability) or to 250 kg N and 6.4 kg P ha-1 (high N and low P availability). Carbon and nitrogen allocation between the symbionts was assessed by exposing the foliage to 14CO2 and the mycelium to 15N-alanine or 15NH4 + simultaneously and measuring the distribution of the isotopic tracers after a three-day chase period. High inorganic N combined with low P availability did not have marked effect on symbiosis-mediated N uptake from alanine, whilst high N and P availability reduced alanine-derived 15N translocation by the fungus to the plant. Shoot 15N concentration and concentration of 14C in the extramatrical mycelium correlated significantly across treatments pointing to controlled reciprocity of transactions between the partners.
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| 20. |
- Nohrstedt, H.Ö., et al.
(författare)
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Changes in carbon content, respiration rate, atp content, and microbial biomass in nitrogen-fertilized pine forest soils in Sweden
- 1989
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Ingår i: Canadian Journal of Forest Research. - : Canadian Science Publishing. - 1208-6037 .- 0045-5067. ; 19:3, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- Carbon content and indices of microbial biomass and activity were determined in 1985 in different soil horizons of two nitrogen-fertilized pine forests in Sweden. The Kroksbo site was fertilized in 1974 with 150 and 600 kg N•ha−1 using NH4NO3 or urea, while the Nissafors site was fertilized in 1977 and 1984 with 150 kg NH4NO3-N•ha−1 The absolute amount of C per square metre of forest floor increased in fertilizer treatments compared with the control (by 10–26%, depending on the site or fertilizer treatment). Respiration rate, ATP content, and microbial biomass C, measured with the substrate-induced respiration technique, decreased in all horizons when expressed per gram of C. The decrease was most evident with NH4NO3, and at the highest level of fertilization. However, on an area basis there were no differences between fertilizer and control treatments. A calculated increase in litter fall in the fertilized plots could not explain all the increase in the amount of C per square metre compared with the control. Decreased microbial activity per gram of C therefore appeared to be an important factor in the increase in C content in fertilized plots.
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| 21. |
- 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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| 22. |
- Wallander, Håkan, et al.
(författare)
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Uptake of N-15-labelled alanine, ammonium and nitrate in Pinus sylvestris L. Ectomycorrhiza growing in forest soil treated with nitrogen, sulphur or lime
- 1997
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Ingår i: Plant and Soil. - 0032-079X. ; 195:2, s. 329-338
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Tidskriftsartikel (refereegranskat)abstract
- The uptake of N-15-labelled alanine, ammonium and nitrate was studied in ectomycorrhizal morphotypes of intact Pinus sylvestris seedlings. PCR-RFLP analysis of the ITS-region of fungal rDNA was used to identify the morphotypes. Seedlings were grown in forest soil collected at an experimental site in southern Sweden. The treatments compared were a control, N fertilisation (600 kg N ha(-1) as urea), sulfur application (1200 kg S ha(-1)) and lime application (6000 kg CaCO3 ha(-1)). The forest, which had been dominated by Picea abies, was clear-cut two years before the forest soil was sampled. Soil was also collected from an adjacent standing forest. The aim of the present study was to detect changes in the ectomycorrhizal communities in forest soils and relate these changes to the functional parameter of uptake of nitrogen from organic (alanine and protein) and inorganic (ammonium and nitrate) sources. Liming resulted in the detection of a morphotype not found in other samples, and one morphotype was only found in samples from the standing forest (the fungi in these two morphotypes could not be identified). All mycorrhizal root tips showed a higher N-15 concentration after exposure to different nitrogen forms than non-mycorrhizal long roots. Uptake of N-15 from a labelled solution of alanine or ammonium was higher (about tenfold) than uptake from a N-15-labelled solution of nitrate. Uptake of ammonium and alanine varied between 0.2 and 0.5 mg N g(-1) h(-1) and between 0.1 and 0.33 mg N g(-1) h(-1), respectively, among the different morphotypes. In seedlings grown in the control soil and in soil from standing forest, alanine and ammonium were taken up to a similar degree from a supply solution by all morphotypes, whereas ammonium uptake was higher than alanine uptake in seedlings grown in lime-treated soil (about twofold) and. to a lesser extent, in the nitrogen-and sulfur-treated soils. The higher ammonium uptake by morphotypes from the limed soil was confirmed in pure culture studies. In cases where ammonium was used as the N source, an isolate of the S. variegatus morphotype collected in the limed soil produced more biomass compared with isolates of S. variegatus collected in nitrogen or sulphur-treated soil. One isolate of a silvery white morphotype produced about equal amounts of biomass on alanine and ammonium, whereas all S. variegatus isolated performed better with ammonium as their N source. Based on the results it is hypothesised that liming can induce a shift in the ectomycorrhizal community, favouring individuals that mainly utilise inorganic nitrogen over those that primarily utilise organic nitrogen
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