Assessment of methylammonium as an analog for ammonium in plant uptake from soil

Jackson, Louise E.; Bloom, Arnold J.

doi:10.1007/bf00010071

Cited by 4 publications

(2 citation statements)

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“…Though 14 C‐labelled methylammonium has been widely used as a transport analogue for NH 4 + in algae (Kleiner 1981) higher plants (Jackson & Bloom 1994; Kosola & Bloom 1994; Kielland 1994) and fungi (Kleiner 1981) some doubts have been expressed about the extent to which its kinetic properties are representative of those observed for NH 4 + . Kosola & Bloom (1994), for example, showed for tomato that although methylammonium and NH 4 + share a common transport system, this system has a far greater affinity for NH 4 + , the K M for the latter being six times lower than for 14 C‐methylammonium.…”

Section: Discussionmentioning

confidence: 99%

Kinetics of amino acid uptake by ectomycorrhizal roots

Wallenda

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1999

Plant Cell & Environment

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It is well established that ectomycorrhizal fungi can use amino acids as nitrogen and carbon sources, but data on the kinetic properties of amino acid uptake systems of ectomycorrhizal systems are scarce. Using 14 C-labelled compounds we have determined the kinetics of uptake of amino acids by excised ectomycorrhizal roots for a range of distinct mycorrhizal types from three tree species, beech, spruce, and pine. All mycorrhizal types examined took up amino acids via high-affinity transport systems (K M values ranging from 19 to 233 mmol m -3 ). A comparative analysis of kinetic parameters for uptake of amino acids and the ammonium analogue methylammonium showed that ectomycorrhizal roots have similar or even higher affinities (lower K M values) for the amino acids, indicating that absorption of these organic forms of nitrogen (N) can contribute significantly to total N uptake by ectomycorrhizal plants. Analysis of amino acid uptake by ectomycorrhizal roots collected along a European north/south gradient of increasing mineral N pollution from northern Sweden to south Germany revealed no obvious trend in the uptake capabilities for amino acids by ectomycorrhizal roots in relation to the location of the sampling site on this gradient. Rather, the fungal species forming a particular morphotype was the factor determining uptake kinetics. It can therefore be deduced that the species composition of the fungal community will contribute significantly to the functional diversity of a population of mycorrhizal roots.

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Section: Discussionmentioning

confidence: 99%

Kinetics of amino acid uptake by ectomycorrhizal roots

Wallenda

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1999

Plant Cell & Environment

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“…which limits its utility for field experiments. On the other hand, the use of analogues such as CI03 (synthesized with 36CI) for N0 3 and CH3NH3 (labeled with 14C) for NHt uptake studies have recently been criticized for not reliably reflecting the uptake behavior of N0 3 and NHt (Jackson and Bloom, 1994;Bloom, 1994, 1996;Siddiqi et al, 1992). More recently, 15N is widely used as a tracer in N uptake studies.…”

Section: Introductionmentioning

confidence: 99%