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Plant function and evolutionary biology
RESEARCH ARTICLE

Amino acids are a nitrogen source for sugarcane

Kerry Vinall A , Susanne Schmidt A , Richard Brackin A , Prakash Lakshmanan B and Nicole Robinson A C
+ Author Affiliations
- Author Affiliations

A School of Agriculture and Food Science, The University of Queensland, Brisbane, Qld 4072, Australia.

B BSES Ltd, 50 Meiers Road, Indooroopilly, Qld 4068, Australia.

C Corresponding author. Email: nicole.robinson@uq.edu.au

Functional Plant Biology 39(6) 503-511 https://doi.org/10.1071/FP12042
Submitted: 7 February 2012  Accepted: 16 April 2012   Published: 15 May 2012

Abstract

Organic forms of nitrogen (ON) represent potential N sources for crops and an alternative to inorganic N (IN, ammonium nitrate). Sugarcane soils receive organic harvest residues (~40–100 kg ON ha–1), but it is unknown whether ON is a direct N source for crops. We investigated whether sugarcane can use organic monomers in the form of amino acids and whether the use of amino acids as a N source results in distinct metabolic or morphological change when compared with use of inorganic N (IN). Plantlets cultivated in sterile culture and young plants grown in non-sterile soil culture were supplied with IN, ON (five amino acids present in sugarcane soils), or combined IN and ON. All treatments resulted in similar biomass and N content indicating that sugarcane has a well developed capacity to use ON and confirms findings in other species. ON-supplied plants in axenic culture had increased total branch root length per unit primary root axis which has not been reported previously. In both experimental systems, ON supplied plants had increased asparagine concentrations suggesting altered N metabolism. Root of ON-supplied soil-grown plants had significantly reduced nitrate concentrations. We interpret the shift from nitrate to asparagine as indicative of N form use other than or in addition to nitrate by sugarcane. N metabolite profiling could advance knowledge of crop N sources and this will aid in development of N efficient cropping systems with a reduced N pollution footprint.

Additional keywords: ammonium, nitrate, organic N, sugarcane production, sustainable.


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