N2-fixation estimated by 15N natural abundance can be erroneous because of changes in 15N-discrimination during N-uptake

Abstract

Determining 15N discrimination(∈) during N2 fixation is a must for the use of 15N natural abundance (NA) to estimate N2 fixation, while ∈ during uptake of mineral N is neglected because of low supply of N the in the field. In the greenhouse a nutrient-solution experiment was run to measure ∈ during sole NO3 nutrition (8 mM) of white lupin (lupNO3), oat and flax. Additionally ∈ was determined for white lupin solely supplied with N2-N (lupN2). Effects of plant age and N distribution within the plant were investigated by sequential harvests and separating the plants into their parts. Besides of strong growth of all plants only lupin reached the reproductive stage. More than double the N acquired by lupNO3 and lupN2 was taken up by oat. Mean ∈P/S [∈ 15N ‰] increased from flax (−3.9) via lupNO3 (−3.1) and oat (−2.4) to lupN2 (−1.5). In oat and flax ∈ oscillated around its mean, no change in lupN2 and showed a steady increase in lupNO3. A close relationship between ∈ and the shoot share to total N gain was found for all treatments. Therefore, N demand from the shoot determined ∈. The impact of these findings for field use of NA is discussed.

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Titel N2-fixation estimated by 15N natural abundance can be erroneous because of changes in 15N-discrimination during N-uptake
Medien Plant Nutrition: Food security and sustainability of agro-ecosystems through basic and applied research
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Verfasser/Herausgeber Prof. Dr. Hauke Heuwinkel, Reinhold Gutser, N. Claassen, Prof. Dr. Urs Schmidhalter
Seiten 654-655
Veröffentlichungsdatum 01.01.2001
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Zitation Heuwinkel, H.; Gutser, R.; Claassen, N.; Schmidhalter, U. (2001): N2-fixation estimated by 15N natural abundance can be erroneous because of changes in 15N-discrimination during N-uptake. Plant Nutrition: Food security and sustainability of agro-ecosystems through basic and applied research, S. 654-655. DOI: 10.1007/0-306-47624-X_317