| 1. |
- Markkola, A. M, et al.
(författare)
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Shift in ectomycorrhizal community composition in Scots pine (Pinus sylvestris L.) seedling roots as a response to nickel deposition and removal of lichen cover
- 2002
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 120:3, s. 797-803
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Tidskriftsartikel (refereegranskat)abstract
- Scots pine seedlings were exposed to wet-deposited nickel (Ni) and removal of lichen cover in a dry heath Scots pine forest. Ni deposition affected the colonization of roots by indigenous ectomycorrhizal fungi in contrasting ways in intact and skimmed quadrats. Highest frequencies of tubercle morphotypes of ectomycorrhiza were found in quadrats exposed to 100 mg m-2 year-1 Ni in lichen covered treatment, while in skimmed quadrats these peaked after the treatment with 10 mg Ni m-2 year-1. Removal of the lichen layer increased the value of diversity index (H′) of ectomycorrhizal fungal community, probably due to the increase in the evenness of the morphotype distribution. Lichen removal seemed also to improve the condition of the short roots, as the frequencies of poor and senescent short roots were decreased by the removal.
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| 2. |
- Roitto, M., et al.
(författare)
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Does the lichen mat alleviate the effects of wet deposited nickel on soil microorganisms and Scots pine (Pinus sylvestris L.) seedlings?
- 2001
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Ingår i: Plant and Soil. - : Kluwer Academic Publishers. - 0032-079X .- 1573-5036. ; 230:2, s. 267-277
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Tidskriftsartikel (refereegranskat)abstract
- A field experiment was conducted in a dry heath forest dominated by Scots pine (Pinus sylvestris L.) and a mat-forming lichen (Cladina stellaris (Opiz) Brodo) to assess the effect of wet-deposited nickel (Ni) on pine seedlings and soil microorganisms, and to explore whether an intact lichen mat could act as a buffer against heavy metal deposits. Pine seedlings were planted in quadrats covered by a natural lichen layer and in quadrats from which the lichen layer had been completely removed. The quadrats were exposed to four levels of Ni deposition: 0 (i.e., distilled water), 10, 100 and 1000 mg m-2 year-1 in two growing seasons. Increasing Ni deposition led to an increase in the Ni content of the needles, roots and the soil organic layer. The lichen mat reduced Ni flow to the organic soil layer, but had no significant, reducing effect on needle or root Ni concentration. The most severe Ni treatment had detrimental effects on seedling growth and increased peroxidase activity in the previous years needles. Removal of the lichen layer did not increase susceptibility of seedlings to Ni. Values of maximal carbon use efficiency (Max) and metabolic quotient (qCO2) of the soil microorganisms indicated protective value of the lichen mat to soil microorganisms at the highest Ni treatment. Skimming per se decreased basal respiration, qCO2 and concentrations of potassium in the soil and also increased the lag period of the microorganisms as a response to in situ substrate addition.
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| 3. |
- Ahonen-Jonnarth, Ulla, et al.
(författare)
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Effects of nickel and copper on growth and mycorrhiza of Scots pine seedlings inoculated with Gremmeniella abietina
- 2004
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Ingår i: Forest Pathology. - : Wiley. - 1437-4781 .- 1439-0329. ; 34:6, s. 337-348
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Tidskriftsartikel (refereegranskat)abstract
- Scots pine (Pinus sylvestris) seedlings were planted in soil originating from two localities with different background levels of nickel and copper. In addition, some of the seedlings were exposed to additional nickel (20.5 mg Ni/l of soil) or copper (63.5 mg Cu/l of soil), or a combination of both Ni and Cu, via soil without direct shoot exposure during their second growing period. The seedlings were either irrigated with spring water (pH 6) or got only natural rain during the whole field experiment. All seedlings were inoculated with conidia of a shoot-pathogen Gremmeniella abietina during their third growing season, and harvested the following spring. Lengths of shoots of different year-classes were used as growth estimates. In roots, the proportion of fungal (assumedly mycorrhizal) biomass was estimated by measuring ergosterol concentration. Guajacol peroxidase activity was measured. Short roots were classified into two groups according to their condition and the composition of the mycorrhizal community was expressed as a proportion of morphotypes in the roots. The seedlings exposed to additional Ni had higher shoot growth than the seedlings in the other treatments. The mean Ni concentration in the roots of seedlings exposed to additional Ni was 79 p.p.m. and in other seedlings 16 p.p.m. Additional Ni also decreased the frequency of clearly senescent short roots and the proportion of the mycorrhizal morphotype with the thinnest mantle. These results indicate that the Ni exposure levels used in this experiment had some positive effects on the seedlings. The relative fungal biomass was about 6% lower (p = 0.0981) in the fine roots of seedlings treated with additional Cu. The mean Cu concentration in the roots of seedlings exposed to additional Cu was 256 p.p.m. and in other seedlings 29 p.p.m. Peroxidase activity, which was used as a general stress indicator in this study, was not affected by any of the treatments. The shoot growth and the relative biomass of fungi in the fine roots were positively correlated in all seedlings, and this correlation was stronger in seedlings exposed to additional Ni that were not irrigated compared with seedlings not exposed to additional Ni that were irrigated. The frequency of asymptomatic infections of G. abietina was positively correlated with the proportion of senescent short roots in the irrigated seedlings but not in not-irrigated seedlings. The general condition of seedlings may be an important factor for infection by G. abietina when moisture is high enough for the fungi to infect seedlings by conidia.
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| 4. |
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| 5. |
- Kuikka, K, et al.
(författare)
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Severe defoliation of Scots pine reduces reproductive investment by ectomycorrhizal symbionts
- 2003
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Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 84:8, s. 2051-2061
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Tidskriftsartikel (refereegranskat)abstract
- Reduction in the photosynthetic capacity of plants is presumed to negatively affect their fungal symbionts. To test this hypothesis under natural conditions, we artificially removed 100% of previous year needles in two successive years on Scots pine trees (Pinus sylvestris L.) to simulate pine sawfly attack. Despite a decline in the shoot growth of defoliated trees, root biomass did not differ from control trees. The ergosterol (fungal biomass) and starch concentration of fine roots, however, slightly declined in defoliated trees. Percent ectomycorrhizal colonization of fine root tips remained high in both defoliated and control trees. The dominant tubercle morphotypes were slightly more abundant in the control than in defoliated trees. In contrast to the relatively weak effects on vegetative ectomycorrhizae, reproduction declined near the defoliated pines. Average sporocarp numbers and, consequently, the relative fungal investment to reproduction of the estimated total fungal biomass were more than three times higher near controls than defoliated trees in the first treatment year. Defoliation also reduced the diversity of ectomycorrhizal species producing sporocarps. Mutualistic fungal symbionts may thus alter their reproductive investment in response to restrictions on host resources. Because fungal biomass in the roots as well as colonization percentage remained unchanged, Scots pine evidently continues to invest in the maintenance of the symbiosis despite the reduced photosynthetic capacity due to defoliation.
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| 6. |
- Roitto, M., et al.
(författare)
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Apoplastic and total peroxidase activities in Scots pine needles at subarctic polluted sites
- 1999
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Ingår i: European journal of forest pathology. - : Blackwell. - 0300-1237. ; 29, s. 399-410
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Tidskriftsartikel (refereegranskat)abstract
- A gradient survey was carried out in order to compare peroxidase activity in Scots pine (Pinus sylvestris) needles in relation to distance from the industrial centre of Monchegorsk, on the Kola Peninsula in north-western Russia. Apoplastic and total peroxidase activity and sulphur (S), nickel (Ni) and copper (Cu) content in the needles of mature trees were measured on seven plots located between 10 and 110 km from the pollution source. Peroxidase activities in both current- and previous-year needles increased towards the smelters and showed a positive correlation with needle S, Cu and Ni concentrations. Total peroxidase activities showed a more obvious relationship to the pollution gradient in winter than in autumn. The element contents in the current year needles averaged 1649 ppm (S), 128 ppm (Ni) and 118 ppm (Cu) close to the smelters, 1212 ppm (S), 37 ppm (Ni) and 67 ppm (Cu) at adistance of 40 km and 831 ppm (S), 7 ppm (Ni) and 1 ppm (Cu) at the most distant sampling plot. This study showed that both the apoplastic and total peroxidase activities responded to heavy metal and sulphur pollution up to 40 km from the smelters in winter, which indicated an increased oxidative stress in this area. The harsh climate conditions and the high pollution levels may have had additive effects. However, as peroxidases are considered a general indicator of stress, it is not possible to evaluate the extent to which single pollutants contribute to this enzyme activity.
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