Competition for amino acids between wheat roots and rhizosphere microorganisms and the role of amino acids in plant n acquisition

A. G. Owen, D. L. Jones

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261 Citations (Scopus)

Abstract

The direct uptake of organic nitrogen compounds from the soil solution by plant roots has been hypothesised to constitute a significant source of N to the plant particularly in N limiting ecosystems. The experiments undertaken here were designed to test whether wheat roots could out-compete the rhizosphere microflora for a pulse addition of organic N in the form of three contrasting amino acids, namely lysine, glycine and glutamate. Amino acids were added at a concentration reflecting reported soil solution concentrations (100 μM) and the uptake into either plant biomass or respiration or microbial biomass and respiration determined over a 24 h chase period. The results showed that the plant roots could only capture on average 6% of the added amino acid with the remainder captured by the microbial biomass. We therefore present direct in vivo evidence to support earlier work which has hypothesised that organic N may be of only limited consequence in high input agricultural systems. We suggest that this is a result of the higher concentrations of NO-3 in agricultural soil solutions, the slow movement of amino acids in soil relative to NO-3, the rapid turnover of amino acids by soil microorganisms, and the poor competitive ability of plant roots to capture amino acids from the soil solution.

Original languageEnglish
Pages (from-to)651-657
Number of pages7
JournalSoil Biology and Biochemistry
Volume33
Issue number4-5
DOIs
Publication statusPublished - 7 Apr 2001
Externally publishedYes

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