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Phosphorus effects on metabolic processes in monoxenic arbuscular mycorrhiza cultures

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Author

Summary, in English

The influence of external phosphorus (P) on carbon (C) allocation and metabolism as well as processes related to P metabolism was studied in monoxenic arbuscular mycorrhiza cultures of carrot (Daucus carota). Fungal hyphae of Glomus intraradices proliferated from the solid minimal medium containing the colonized roots into C-free liquid minimal medium with different P treatments. The fungus formed around three times higher biomass in P-free liquid medium than in medium with 2.5 mM inorganic P (high-P). Mycelium in the second experiment was harvested at an earlier growth stag to study metabolic processes when the mycelium was actively growing. P treatment influenced the root P content and [C-13]glucose administered to the roots 7 d before harvest gave a negative correlation between root P content and C-13 enrichment in arbuscular mycorrhiza fungal storage lipids in the extraradical hyphae. Eighteen percent of the enriched C-13 in extraradical hyphae was recovered in the fatty acid 16:1omega5 from neutral lipids. Polyphosphate accumulated in hyphae even in P-free medium. No influence of P treatment on fungal acid phosphatase activity was observed, whereas the proportion of alkaline-phosphatase-active hyphae was highest in high-P medium. We demonstrated the presence of a motile tubular vacuolar system in G. intraradices. This system was rarely seen in hyphae subjected to the highest P treatment. We concluded that the direct responses of the extraradical hyphae to the P concentration in the medium are limited. The effects found in hyphae seemed instead to be related to increased availability of P to the host root.

Publishing year

2002

Language

English

Pages

1162-1171

Publication/Series

Plant Physiology

Volume

130

Issue

3

Document type

Journal article

Publisher

American Society of Plant Biologists

Topic

  • Ecology

Status

Published

Research group

  • Microbial Ecology
  • Plant Biology

ISBN/ISSN/Other

  • ISSN: 1532-2548