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Acquisition and assimilation of nitrogen as peptide-bound and D-enantiomers of amino acids by wheat

Hill, Paul. W.; Quilliam, Richard. S.; DeLuca, Thomas. H.; Farrar, John; Farrell, Mark; Roberts, Paula; Newsham, Kevin; Hopkins, David. W.. 2011 Acquisition and assimilation of nitrogen as peptide-bound and D-enantiomers of amino acids by wheat. Plos One, 6 (4). 4, pp. 10.1371/journal.pone.0019220

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Abstract/Summary

Nitrogen is a key regulator of primary productivity in many terrestrial ecosystems. Historically, only inorganic N (NH4+ and NO3-) and L-amino acids have been considered to be important to the N nutrition of terrestrial plants. However, amino acids are also present in soil as small peptides and in D-enantiomeric form. We compared the uptake and assimilation of N as free amino acid and short homopeptide in both L- and D-enantiomeric forms. Sterile roots of wheat (Triticum aestivum L.) plants were exposed to solutions containing either 14C-labelled L-alanine, D-alanine, L-trialanine or D-trialanine at a concentration likely to be found in soil solution (10 µM). Over 5 h, plants took up L-alanine, D-alanine and L-trialanine at rates of 0.9±0.3, 0.3±0.06 and 0.3±0.04 µmol g−1 root DW h−1, respectively. The rate of N uptake as L-trialanine was the same as that as L-alanine. Plants lost ca.60% of amino acid C taken up in respiration, regardless of the enantiomeric form, but more (ca.80%) of the L-trialanine C than amino acid C was respired. When supplied in solutions of mixed N form, N uptake as D-alanine was ca.5-fold faster than as NO3-, but slower than as L-alanine, L-trialanine and NH4+. Plants showed a limited capacity to take up D-trialanine (0.04±0.03 µmol g−1 root DW h−1), but did not appear to be able to metabolise it. We conclude that wheat is able to utilise L-peptide and D-amino acid N at rates comparable to those of N forms of acknowledged importance, namely L-amino acids and inorganic N. This is true even when solutes are supplied at realistic soil concentrations and when other forms of N are available. We suggest that it may be necessary to reconsider which forms of soil N are important in the terrestrial N cycle.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1371/journal.pone.0019220
Programmes: BAS Programmes > Polar Science for Planet Earth (2009 - ) > Ecosystems
Additional Information. Not used in RCUK Gateway to Research.: Open access article made available under a CC-BY Creative Commons Attribution license.
NORA Subject Terms: Ecology and Environment
Date made live: 26 Oct 2011 16:28
URI: http://nora.nerc.ac.uk/id/eprint/15614

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