Nitrogen uptake and growth in vitro by Hebeloma crustuliniforme and other Pacific Northwest mycorrhizal fungi

Abstract

Since little is known about the nitrogen (N) physiology of ectomycorrhizal fungi, this study was initiated to study both radial and biomass growth and N uptake of Hebeloma crustuliniforme and other Pacific Northwest ectomycorrhizal fungi. Hebeloma crustuliniforme utilized either nitrate or ammonium as the N source in buffered liquid media, but biomass growth was greatest with ammonium. Without buffers, biomass growth on ammonium-based media was reduced, apparently owing to low pH. These results emphasize the strong interrelationship between N source and pH of the media. A pronounced pH optimum for biomass growth of H. crustuliniforme occurred at pH 5.0. Ammonium uptake rates were five to nine times greater than nitrate uptake rates over a range of N concentrations (40–600 μM). Radial growth rates of a range of mycorrhizal fungi were greater on high-N than on low-N media. For those few species that grew faster on low-N medium, their growth habit was more diffuse and dry weight production was decreased, indicating that radial growth had occurred at the expense of biomass production.

Compartmentation and flux characteristics of ammonium in spruce

“…While the assumption that a poor utilization capacity for nitrate is a characteristic trait of woody as opposed to herbaceous species represents an incorrect generalization (Stadler and Gebauer 1992), a pronounced preference for ammonium over nitrate does appear to be systemic in many coniferous species (Kronzucker et al 1995a, and references therein). Interestingly, this preference seems to be shared by the ectomycorrhizal fungi normally colonizing the roots of these species in the field (Littke 1982;Littke et al 1984;Rygiewicz et al 1984a, b;Lang and Jagnow 1986).…”

Growth characteristics, nitrogen uptake and enzyme activities of the nitrate-utilising ectomycorrhizal Scleroderma verrucosum

“…that is eight times higher than NO $ − uptake (39 µmol g −" h −" ..) (Littke, Bledsoe & Edmonds, 1984). In contrast, for C. geophilum, NH % + uptake was lower (19 µmol g −" h −" ..)…”

“…According to those authors, however, other fungi such as Cenococcum geophilum, Thelephora terrestris, Laccaria laccata, Hebeloma crustuliniforme and Piloderma croceum grew better on ammonium. For H. crustuliniforme, the biomass production in non-buffered media was reduced due to the low pH (Littke, Bledsoe & Edmonds, 1984). Laccaria proxima, Paxillus involutus (Finlay, Frostegard & Sonnerfeldt, 1992), Pisolithus tinctorius and Suillus granulatus (France & Reid, 1984) grew equally well on nitrate or ammonium.…”

Growth and mineral nutrition of non‐mycorrhizal and mycorrhizal Norway spruce (Picea abies) seedlings grown in semi‐hydroponic sand culture

“…Higher uptake rates of ammonium than of nitrate are a general characteristic of forest trees (Alexander, 1983 ;Marschner, Haussling & George, 1991) as well as of mycorrhizal fungi (Littke et aL, 1984;Scheromm et aL, 1990). Inhibition of nitrate uptake by ammonium is also commonly observed in tree…”

“…4) and needle N concentrations (Tables 4, 5) w-hich occurred in mycorrhizal plants with P. tinctorius but not m mycorrhiza] plants with P. involutus and L. laccata, indicate that the stimulating mycorrhizal effect on nutrient uptake depends on the species of mycorrhizal fungi. Large differences in N uptake rates also exist between different species of mycorrhizal fungi grown ?« vitro (Littke et al, 1984) and between different strains of the same mycorrhizal fungus (Kieliszewska-Rokicka, 1992).…”