Use of inorganic and organic nitrogen sources by sugarcane.

Kerry Vinall (2010). Use of inorganic and organic nitrogen sources by sugarcane. MPhil Thesis, School of Biological Sciences, The University of Queensland.

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Author Kerry Vinall
Thesis Title Use of inorganic and organic nitrogen sources by sugarcane.
School, Centre or Institute School of Biological Sciences
Institution The University of Queensland
Publication date 2010-03
Thesis type MPhil Thesis
Total pages 62
Total colour pages 5
Total black and white pages 57
Subjects 06 Biological Sciences
Abstract/Summary Globally, approximately 100 million tonnes (1011 kg) of synthetic nitrogen (N) fertiliser is applied in agricultural cropping annually. Plant recovery of applied N fertiliser across high production systems averages 50%, and excess N lost from agricultural systems produces greenhouse gases, pollutes waterways and aquifers, causing eutrophication and threatening human health, and is implicated in biodiversity loss. Problems associated with N losses are particularly pertinent to the Australian sugarcane industry, due to the proximity of cropping to environmentally sensitive areas including rainforest and the Great Barrier Reef. The aim of this study was to examine the use of organic and inorganic N forms by sugarcane, a fast-growing tropical crop, to better understand the physiology of N acquisition in the context of soil N forms. Using plantlets grown in sterile agar culture, I show that sugarcane has a well developed capacity to acquire and assimilate amino acids, and that increased tissue concentrations of asparagine are associated with the use of amino acids as N source. Increased tissue concentrations of asparagine were also detected with amino acid supply in soil-grown plants, which may indicate direct uptake of amino acids from soil. To examine N source preferences of field-grown sugarcane, excised and attached roots were incubated in equimolar solutions of ammonium, nitrate and glycine. The nitrogen source preference of field-grown sugarcane was ammonium > glycine > nitrate, with ammonium accounting on average for 62% of total uptake, glycine for 24% and nitrate for only 14%. If the observed discrimination by sugarcane against nitrate is confirmed to be widespread amongst sugarcane genotypes and cropping areas, this trait could be a key reason for the losses of N from sugarcane cropping via leaching and denitrification of nitrate. Knowledge gained here contributes to the understanding of N uptake physiology in sugarcane and will help to inform the design of an efficient sugarcane agronomy which maximises plant N recovery.
Keyword amino acids
organic nitrogen uptake
source preference
Additional Notes Pages of document: 1, 19, 26, 37, 43 Pages numbers as shown in thesis: Title, 11, 18, 29, 35

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Created: Fri, 24 Dec 2010, 14:17:52 EST by Ms Kerry Vinall on behalf of Library - Information Access Service