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Quantitative analysis of root and ectomycorrhizal exudates as a response to Pb, Cd and As stress
Örebro University, School of Science and Technology. (MTM)
Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences.
Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences.
Örebro University, School of Science and Technology. (MTM)
2008 (English)In: Plant and Soil, ISSN 0032-079X, E-ISSN 1573-5036, Vol. 313, no 1-2, 39-54 p.Article in journal (Refereed) Published
Abstract [en]

We examined exudation of low molecular weight (LMW) organic compounds of ectomycorrhizal (ECM) and non-mycorrhizal (NM) seedlings in relation to metals. Scots pine seedlings, either colonized by one of six different ECM fungi or NM, were grown in Petri dishes containing glass beads and liquid growth medium and exposed to elevated concentrations of Pb, Cd and As. Exudation of LMW organic compounds (LMW organic acids (LMWOAs), amino acids and dissolved monosaccharides) and dissolved organic carbon (DOC) was determined qualitatively and quantitatively and exudation rates were calculated. Metals had a significant impact on exudation, especially of oxalate. For Pb and Cd treatments, exudation of oxalate and total LMWOAs generally increased by 15–45% compared to nutrient controls. Production of amino acids, dissolved monosaccharides and DOC was not significantly stimulated by exposure to metals; however, there were non-significant trends towards increased exudation. Finally, exudation generally increased in the presence of mycorrhizal seedlings compared to NM seedlings. The results suggest that ECM fungi may reduce the toxicity of metals to plants through significant increases in the production of organic chelators. Axenic conditions are required to assess the full potential for production of these molecules but their overall significance in soil ecosystems needs to be determined using additional experiments under more ecologically realistic conditions.

Place, publisher, year, edition, pages
Berlin: Springer , 2008. Vol. 313, no 1-2, 39-54 p.
Keyword [en]
amino acids, 13C, carbon cycle, ectomycorrhiza, elevated CO2, exudation, DOC, LMWOA, metal stress, monosaccharides, oxalate, Pinus sylvestris, saprotrophic fungi, soil respiration
National Category
Natural Sciences Environmental Sciences
Research subject
Environmental Chemistry
Identifiers
URN: urn:nbn:se:oru:diva-11842DOI: 10.1007/s11104-008-9678-1OAI: oai:DiVA.org:oru-11842DiVA: diva2:351645
Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Impact of root and mycorrhizal exudation on soil carbon fluxes: influence of elevated CO2 and metals
Open this publication in new window or tab >>Impact of root and mycorrhizal exudation on soil carbon fluxes: influence of elevated CO2 and metals
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The thesis concerns the behavior of root and ectomycorrhizal (ECM) exudates. In particular, the dynamics of soluble low molecular weight (LMW) organic compounds such as organic acids (LMWOAs), amino acids, monosaccharides, and dissolved organic carbon (DOC) have been studied. Our knowledge of exudation rates for tree roots and especially associated ECM is limited, and also factors influencing exudation rates. Two environmental factors, metal stress and elevated atmospheric CO2 level, have been investigated. Both are of great environmental concern, but function in different ways (detoxification and C allocation) and may be highly important for the C flux caused by root/ECM exudation. The project has been carried out with mycorrhizal and nonmycorrhizal (NM) Scots pine seedlings, or saprotrophic fungi, under both sterile and non-sterile (soil) conditions. Analytical determination of exudates and calculation of exudation rates have been major tools for assessment. Assessing the possibility of using naturally occurring chelating agents (e.g. citrate and oxalate) for bioremediation of metals contaminated soils and development and validation of analytical techniques have been additional foci. The results show that from soil-living fungi and ectomycorrhizal roots exudation rates of especially LMWOAs increase significantly at Cd and Pb stress (1-100 μM), while As (as arsenate) and mixtures of metals with As have little effect. The impact of ECM fungi is large and much higher exudation rates are found when the symbionts are present both for controls and metal treatments compared to NM plants. In soil systems there was a significant mobilization of metals from soils under presence of saprotrophic fungi. Both N as well as elevated CO2 (700 ppm) causes sizable increases in exudation rates, independent of biomass, and is a finding that suggests that the availability of easily degradable carbon in soil raises, which may be highly important for the carbon flux in soil. Mycorrhizal seedlings (10 months old) increased total soil respiration ~50% compared to controls without plants in non-sterile soil systems. Key words: amino acids, 13C, carbon cycle, ectomycorrhiza, elevated CO2, exudation, DOC, LMWOA, metal stress, monosaccharides, oxalate, Pinus sylvestris, saprotrophic fungi, soil respiration

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2009. 68 p.
Series
Örebro Studies in Environmental Science, ISSN 1650-6278 ; 14
Keyword
amino acids, 13C, carbon cycle, ectomycorrhiza, elevated CO2, exudation, DOC, LMWOA, metal stress, monosaccharides, oxalate, Pinus sylvestris, saprotrophic fungi, soil respiration
National Category
Natural Sciences Environmental Sciences
Research subject
Enviromental Science
Identifiers
urn:nbn:se:oru:diva-11848 (URN)978-91-7668-692-8 (ISBN)
Public defence
2009-11-13, Hörsal HSM, Fakultetsgatan 1, Örebro, 11:15 (English)
Opponent
Supervisors
Available from: 2010-09-15 Created: 2010-09-15 Last updated: 2017-10-18Bibliographically approved

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Johansson, Emma M.van Hees, Patrick A. W.

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