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Environmental problems - Chemical approaches
RESEARCH ARTICLE

Biofuel ash addition increases ectomycorrhizal fungal exudation in pure culture

Ana Paola Vilches https://orcid.org/0000-0002-9557-3367 A C , Sara H. Norström A , Madelen A. Olofsson A , Petra Fransson B and Dan Bylund A
+ Author Affiliations
- Author Affiliations

A Department of Natural Sciences, Mid Sweden University, SE-851 70 Sundsvall, Sweden.

B Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, SE-750 07 Uppsala, Sweden.

C Corresponding author. Email: ana-paola.vilches@miun.se

Environmental Chemistry 15(8) 481-492 https://doi.org/10.1071/EN18146
Submitted: 3 July 2018  Accepted: 6 October 2018   Published: 31 October 2018

Environmental context. Spreading recycled wood ash in forests may counteract acidification and nutrient losses, but the process may also affect symbiotic fungi in these eco-systems. We show how fungal species react when exposed to ash solutions; for example, by an increased release of organic acids and other compounds. These effects can influence pH and metal availability in forest soils treated with ash.

Abstract. Recycling of wood ash may counteract acidification and losses of base cations resulting from whole-tree harvesting in boreal forest ecosystems. The effects of ash treatment on growth and exudation of eight ectomycorrhizal fungal species were investigated in this study. Six basidiomycetes and two ascomycetes were grown in liquid pure culture with different levels of ash amendments. Biomass production, pH and the exudation of 17 low-molecular-mass organic acids (LMMOAs), 23 amino acids (AAs) and 9 hydroxamate siderophores (HSs) were recorded after 1, 2 and 4 weeks of incubation. Ash did not affect fungal growth, but resulted in higher exudation of the investigated compounds, in particular LMMOAs. Ash also influenced the composition of the exudates. We measured exudation of LMMOAs and AAs up to millimolar and micromolar concentrations respectively. For example, Rhizopogon roseolus mainly produced oxalic acid, whereas Lactarius rufus and Tomentellopsis submollis produced the highest concentrations of AAs. Ferricrocin, the only HS detected, was exuded at the nanomolar level. Exudation responses were also highly species-dependent, e.g. the ascomycetous isolates that produced the largest biomass released low amounts of exudates compared with the basidiomycetes, and were the only ones producing siderophores. This growth–exudation response to ash is likely a trade-off in carbon allocation whereby the mycorrhizal fungal species invest carbon in either higher biomass production or higher exudation.

Additional keywords: mass spectrometry, metabolomics, metal stress, soil acidification.


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