| 1. |
- Ekblad, Alf, et al.
(författare)
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Chitin and ergosterol combined to measure total and living fungal biomass in ectomycorrhizas
- 1998
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 138:1, s. 143-149
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the chitin and ergosterol contents of ectomycorrhizal roots in three sets of experiments to evaluate them as indicators of fungal biomass. The first set of experiments showed that ageing had a marked effect on ergosterol concentrations. The ergosterol content of 7-month-old, brown, shrunken Pinus sylvestris L.–Paxillus involutus (Fr.) Fr. mycorrhizas was found to be only 10% of that found in white, turgid, 1- or 4-month-old specimens. This supports the hypothesis that the compound is a good indicator of living fungal biomass. Ageing had a lesser effect on chitin concentrations since the chitin levels found in 7-month-old mycorrhizas were still 60% of the levels found in 1- and 4-month-old specimens.Consequently, the chitin∶ergosterol ratio increased from about 14 to 19 in 1- and 4-month-old mycorrhizas respectively to about 110 in 7-month-old mycorrhizas. In the second set of experiments, we found that variation in plant growth had no effect on the chitin∶ergosterol ratio in whole root systems of either Alnus incana (L.) Moench or Pinus sylvestris mycorrhizal with Paxillus involutus. In the third set of experiments, we found a constant relationship between the two marker concentrations in 10-month-old root systems of Pinus sylvestris, regardless of fungal species involved, using Paxillus involutus, Piloderma croceum Erikss. & Hjorts and Suillus variegatus (Fr.) O. Kuntze as test organisms. Taken together, the results of this study suggest that both chitin and ergosterol give reliable, but different, relative measures of fungal biomass in mycorrhizal roots. Furthermore, we demonstrate that, in combination, the two chemical markers can be used to estimate both total and living fungal biomass (derived from the chitin∶ergosterol ratio).
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| 2. |
- Ekblad, Alf, 1957-, et al.
(författare)
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Determination of chitin in fungi and mycorrhizal roots by an improved HPLC analysis of glucosamine
- 1996
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Ingår i: Plant and Soil. - 0032-079X .- 1573-5036. ; 178:1, s. 29-35
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Tidskriftsartikel (refereegranskat)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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| 3. |
- Högberg, Peter, et al.
(författare)
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Nitrogen isotope fractionation during nitrogen uptake by ectomycorrhizal and non-mycorrhizal Pinus sylvestris
- 1999
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 142:3, s. 569-576
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Tidskriftsartikel (refereegranskat)abstract
- An experiment was performed to find out whether ectomycorrhizal (ECM) fungi alter the nitrogen (N) isotope composition, δ15N, of N during the transport of N from the soil through the fungus into the plant. Non- mycorrhizal seedlings of Pinus sylvestris were compared with seedlings inoculated with either of three ECM fungi, Paxillus involutus, Suillus bovinus and S. variegatus. Plants were raised in sand in pots supplied with a nutrient solution with N given as either NH4+ or NO3−. Fractionation against 15N was observed with both N sources; it decreased with increasing plant N uptake, and was larger when NH4+ was the source. At high ratios of Nuptake/Nsupplied there was no (NO3−), or little (NH4+), fractionation. There seemed to be no difference in fractionation between ECM and non-mycorrhizal plants, but fungal rhizomorphs were sometimes enriched in 15N (up to 5‰ at most) relative to plant material; they were also enriched relative to the N source. However, this enrichment of the fungal material was calculated to cause only a marginal decrease (−0.1‰ in P. involutus) in δ15N of the N passing from the substrate through the fungus to the host, which is explained by the small size of the fungal N pool relative to the total N of the plant, i.e. the high efficiency of transfer. We conclude that the relatively high 15N abundance observed in ECM fungal species should be a function of fungal physiology in the ECM symbiosis, rather than a reflection of the isotopic signature of the N source(s) used. This experiment also shows that the δ15N of plant N is a good approximation of δ15N of the available N source(s), provided that N is limiting growth.
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| 4. |
- Näsholm, Torgny, et al.
(författare)
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Boreal forest plants take up organic nitrogen
- 1998
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 392:6679, s. 914-916
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Plant growth in the boreal forest, the largest terrestrial biome, is generally limited by the availability of nitrogen. The presumed cause of this limitation is slow mineralization of soil organic nitrogen1,2. Here we demonstrate, to our knowledge for the first time, the uptake of organic nitrogen in the field by the trees Pinus sylvestris and Picea abies, the dwarf shrub Vaccinium myrtillus and the grass Deschampsia flexuosa. These results show that these plants, irrespective of their different types of root–fungal associations (mycorrhiza), bypass nitrogen mineralization. A trace of the amino acid glycine, labelled with the stable isotopes 13C and 15N, was injected into the organic (mor) layer of an old successional boreal coniferous forest. Ratios of 13C:15N in the roots showed that at least 91, 64 and 42% of the nitrogen from the absorbed glycine was taken up in intact glycine by the dwarf shrub, the grass and the trees, respectively. Rates of glycine uptake were similar to those of 15N-ammonium. Our data indicate that organic nitrogen is important for these different plants, even when they are competing with each other and with non-symbiotic microorganisms. This has major implications for our understanding of the effects of nitrogen deposition, global warming and intensified forestry.
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| 5. |
- Sundberg, Bodil, et al.
(författare)
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Lichen respiration in relation to active time, temperature, nitrogen and ergosterol concentrations
- 1999
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 13:1, s. 119-125
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Tidskriftsartikel (refereegranskat)abstract
- Summary1.Respiration in eight lichen species was related to thallus hydration status, externaltemperature and to total nitrogen, chitin and ergosterol concentrations. Chitin is anitrogenous and major compound of the fungal cell wall, and ergosterol is a sterol ofthe plasma membrane in fungi and sometimes in algae.2.Hydration of previously dry thalli resulted in an initially high rate of respiration.Both the amplitude of this resaturation respiration and the time required to reachsteady state varied among species. Generally, peak rates were one to three times higherthan steady-state rates, which were reached 3–7 h after hydration.3.Increases in external temperature also resulted in transient bursts in respiration.Again, both the amplitude of the burst and the time required to reach steady statevaried among species. Also depending on species, a temperature increase from 5 to 15 °Cresulted in two- to fivefold increases in steady-state respiration.4.Steady-state respiration, at optimal thallus hydration and a given temperature,varied three- to sixfold among the species, when related to thallus dry mass. This dif-ference correlated best (r2= 0·89) with their ergosterol concentration, where adoubling in ergosterol resulted in more than a doubling in respiration. Respirationcorrelated less well to total nitrogen or chitin.5.The chitin to ergosterol ratio varied more than one order of magnitude between thespecies, where species with high nitrogen concentrations had the highest ratio. Thisimplies that species with access to ample amounts of nitrogen can make more fungalcell walls in relation to plasma membrane surface area.
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| 6. |
- Westling, Olle, et al.
(författare)
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Kväveomsättning och skogstillstånd i observationsytan Östra Mörtnäs, Värmland
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Integrerande undersökningar som bland annat omfattar undersökningar av deposition av luftföroreningar, markvattenkvalitè, markkemi, och barrutglesning utförs i permanenta skogsytor över hela Sverige. Ett fåtal undersökta skogsytor i landet avviker från det generella dos/respons-mönstret genom att uppvisa tecken på framför allt onormal kväveomsättning, trots att belastningen av kväve i form av luftföroreningar är relativt liten eller måttlig. En provtagningspunkt med denna karaktär är en granskogsyta i sydvästra Värmland. Östra Mörtnäs. Det dygt nittioåriga granbeståndet växer på relativt bördig mark och inga yttre faktorer är påtagliga som kan förklara den onormala kväveomsättningen som har identifierats genom förhöjda kvävehalter i krondropp och markvatten. Fördjupade studier av trädens tillväxt och barrkemi samt rotröteförekomst i denna skogsyta bedömdes som viktiga för att öka kunskapen om de 'miljöindikatorer' (olika variabler i deposition och markvattnet) som används för att beskriva miljötillståndet.
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