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Plant uptake of dual-labeled organic N biased by inorganic C uptake: Results of a triple labeling study |
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| Authors: | Jim Rasmussen Leopold Sauheitl Yakov Kuzyakov |
| Institution: | a Department of Agroecology and Environment, Faculty of Agricultural Sciences, Aarhus University, Denmark b Soil Physics Section, University of Bayreuth, Germany c Department of Agroecosystem Research, University of Bayreuth, Germany |
| Abstract: | Direct plant uptake of organic nitrogen (N) is often studied using the dual-labeling approach (15N + 13C or 15N + 14C). However, the method might be hampered by uptake of labeled inorganic carbon (C) produced by mineralization of labeled organic compounds. Here we report the results from a triple labeling experiment (15N + 13C + 14C) investigating whether root uptake of labeled inorganic C can bias the results obtained in studies of organic N uptake using dual-labeled amino acids (15N, 13C). In a rhizosphere tube experiment we investigated 13C and 14C uptake by maize either supplied with labeled glycine or  , but found no differences in uptake rates between these C-sources. The uptake of inorganic C to the shoot tissue was higher for maize grown in full light compared to shading, which indicates a passive uptake of inorganic C with water. We conclude that uptake of inorganic C produced by mineralization of amino acids can significantly bias the interpretations of organic N uptake studies using dual-labeling. |
| Keywords: | Organic N uptake Amino acid Inorganic C Dual-labeling 14C 13C 15N |
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