| 1. |
- Ekblad, Alf, 1957-, et al.
(author)
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Determination of chitin in fungi and mycorrhizal roots by an improved HPLC analysis of glucosamine
- 1996
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In: Plant and Soil. - 0032-079X .- 1573-5036. ; 178:1, s. 29-35
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Journal article (peer-reviewed)abstract
- A method to measure chitin content in fungi and ectomycorrhizal roots with high-performance liquid chromatography (HPLC) was developed. Measurements of fluorescence of 9-fluorenylmethylchloroformate (FMOC-CI) derivatives of glucosamine were made on acid hydrolysates of pure chitin, chitin-root mixtures and fungal-root mixtures. The method was applied on 5 isolates of ectomycorrhizal fungi, and ectomycorrhizal and non-mycorrhizal Pinus sylvestris roots. Interference from amino acids was removed by pre-treatment of samples with 0.2 N NaOH. This pre-treatment did not reduce the recovery of chitin, nor did plant material affect the recovery of chitin. The HPLC method was compared with a colorimetric chitin-method by measurements on root-fungal mixtures, with known fungal content. The HPLC method gave estimates of fungal biomass which were equal to the expected while the colorimetric method showed values significantly (p<0.001) lower than the expected. The present chitin method offers a sensitive and specific tool for the quantification of chitin in fungi and in ectomycorrhizal roots.
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| 2. |
- Ekblad, Alf, 1957-, et al.
(author)
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Fungal biomass in roots and extramatrical mycelium in relation to macronutrients and plant biomass of ectomycorrhizal Pinus sylvestris and Alnus incana
- 1995
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 131:4, s. 443-451
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Journal article (peer-reviewed)abstract
- SummaryWe studied the effects of macronutrients on the production and distribution of fungal biomass and plant biomass in ectomycorrhizal (Paxillus involutus (Fr.) Fr.) or non-mycorrhiza] Pinus sylvestris L, and Alnus incana (L.) Moench. Fungal biomass was measured as ergosterol content in roots and extramatrical mycelium, Alnus infants was nodulated with Frankia. All six macronutrients were varied according to a two-level fractional factorial design, The plants were grown in pots during two growing periods in a growth chamber. Levels of N, P and sometimes K and interactions between them, had highly significant effects, whereas Ca. Mg and S had no significant effects. The production of extramatrical mycelial biomass peaked when P was low and other nutrients were high. This investment in extramatrical mycelium resulted in a 660%, higher biomass in mycorrhizal compared with non-mycorrhizal P. sylvestris at this nutrient regime. The proportion of fungal biomass in roots was stable in P. sylvestris hut more variable in A. incana. Alnus incana grew less when mycorrhizal then when non-mycorrhizal. The growth responses to mycorrhiza and to the different nutrient treatments were evident at the end of the first growing period. Non-mycorrhizal P. sylvestris did not respond to P limitation by a production of proportionally more roots. This might be a reflection of an obligate dependency on mycorrhiza for effective P uptake. By contrast, the root/shoot ratio in both mycorrhizal and non-mycorrhiza] P. sylvestris decreased strongly in response to increased N. The opposite root/shoot response was found in Alnus incana, and the ratio decreased strongly in response to increased P and increased in response to increased N.
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| 3. |
- Ekblad, Alf, 1957-, et al.
(author)
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Nitrogen fixation by Alnus incana and nitrogen transfer from A-incana to Pinus sylvestris influenced by macronutrients and ectomycorrhiza
- 1995
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In: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 131:4, s. 453-459
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Journal article (peer-reviewed)abstract
- The aims of this study were to evaluate the effect of macronutrients on nitrogen fixation in mycorrhizal and non-mycorrhizal grey alder (Alnus incana (L.) Moench), and to evaluate the effect of ectomycorrhizal mycelium on the transfer of symbolically fixed nitrogen from grey alder to Scots pine (Pinus sylvestris L). One alder and one pine were grown together in pots with root systems separated by a 20μm mesh nylon filter which allowed hyphae but not roots to penetrate. Half the plants of both species were inoculated with Paxillus involutus (Ft.) Ft. and all alders were inoculated with Frankia. Nutrient solutions were added with macronutrient (N, K, P, Ca, Mg and S) concentrations varied according to a two-level fractional factorial design. The plants were harvested after two growing periods in a growth chamber. Nitrogen fixation by alder and transfer of symbiotically fixed N from alder to pine was measured by 15N-dilution. Fixed N (mg) correlated with nodule biomass in both mycorrhizal and non-mycorrhizal alders. On average, specific nodule activity over the two periods was 510 mg N fixed R' nodule d. wt. This was not affected by mycorrhizal infection or by the different nutrient treatments. By contrast there was a strong nutrient effect on the proportion of N derived from fixation. These results indicate that the regulation of nitrogen fixation was via nodule growth rather than via nodule specific activity. Nitrogen had a strong negative effect and P a positive effect on the percentage of N derived from fixation (%Ndfa). However, the effect of N depended on the level of P. This N × P interaction resulted in a %Ndfa when N was high, of 5-10%, at low P and 45–48%, at high P. The highest value of 90% Ndfa was found at the combination of low N and high P. Potassium had a small but statistically significant effect on the %Ndfa but Ca, Mg and S had no significant effects. No mycorrhizal effect was found on the %Ndfa in alder. By contrast, the %Ndfa and biomass were lower in mycorrhizal than in non-mycorrhizal alders. The proportion of fixed N in pine, transferred from alder, was greatest (9%) when the pine was nitrogen starved and mycorrhizal and the alder was fixing maximally (low N and high P). However, the amount of fixed N transferred to pine was not statistically different from zero.
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| 4. |
- Högberg, Peter, et al.
(author)
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Substrate-induced respiration measured in situ in a C-3-plant ecosystem using additions of C-4-sucrose
- 1996
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In: Soil Biology and Biochemistry. - : Elsevier BV. - 0038-0717 .- 1879-3428. ; 28:9, s. 1131-1138
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Journal article (peer-reviewed)abstract
- We added sucrose derived from sugar cane, a tropical C4-plant, to the soil of a temperate C3-forest plant system. The combined measurement of CO2 respiration rate and 13C natural abundance of CO2 enabled a distinction to be made between C3- and C4-respiration, which offered new possibilities to analyze basal respiration and substrate-induced respiration (SIR) in the field. In tests in the laboratory, through-flow systems were used, while in the field the stationary gas phase under soil covers was sampled. Results from the laboratory and in the field were similar with an average SIR response of 2.2 (range 1.7–2.7) times the basal respiration. The change in δ13C after addition of C4-surcrose was less than expected from the increase in respiration rate. Calculations showed that there was an increased efflux of C3-carbon after the C4-sucrose addition. We describe mathematical models, by which we calculated the various source effects contributing to the measured response. The method has numerous advantages, e.g. it uses naturally labelled inexpensive non-hazardous compounds and measurements are non-destructive to the studied system.
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