Direct raman spectroscopic measurements of biological nitrogen fixation under natural conditions: An analytical approach for studying nitrogenase activity

Jochum T, Fastnacht A, Trumbore SE, Popp J, Frosch T (2017)

Publication Type: Journal article

Publication year: 2017

Journal

Analytical Chemistry American Chemical Society

Book Volume: 89

Pages Range: 1117-1122

Journal Issue: 2

DOI: 10.1021/acs.analchem.6b03101

Abstract

Biological N2 fixation is a major input of bioavailable nitrogen, which represents the most frequent factor limiting the agricultural production throughout the world. Especially, the symbiotic association between legumes and Rhizobium bacteria can provide substantial amounts of nitrogen (N) and reduce the need for industrial fertilizers. Despite its importance in the global N cycle, rates of biological nitrogen fixation have proven difficult to quantify. In this work, we propose and demonstrate a simple analytical approach to measure biological N2 fixation rates directly without a proxy or isotopic labeling. We determined a mean N2 fixation rate of 78 ± 5 μmol N2 (g dry weight nodule)^-1 h^-1 of a Medicago sativa-Rhizobium consortium by continuously analyzing the amount of atmospheric N2 in static environmental chambers with Raman gas spectroscopy. By simultaneously analyzing the CO2 uptake and photosynthetic plant activity, we think that a minimum CO2 mixing ratio might be needed for natural N2 fixation and only used the time interval above this minimum CO2 mixing ratio for N2 fixation rate calculations. The proposed approach relies only on noninvasive measurements of the gas phase and, given its simplicity, indicates the potential to estimate biological nitrogen fixation of legume symbioses not only in laboratory experiments. The same methods can presumably also be used to detect N2 fluxes by denitrification from ecosystems to the atmosphere. (Figure Presented).

Involved external institutions

Leibniz-Institut für Photonische Technologien e.V.

Germany (DE) Max-Planck-Institut für Biogeochemie / Max Planck Institute for Biogeochemistry

Germany (DE)

How to cite

APA:

Jochum, T., Fastnacht, A., Trumbore, S.E., Popp, J., & Frosch, T. (2017). Direct raman spectroscopic measurements of biological nitrogen fixation under natural conditions: An analytical approach for studying nitrogenase activity. Analytical Chemistry, 89(2), 1117-1122. https://doi.org/10.1021/acs.analchem.6b03101

MLA:

Jochum, Tobias, et al. "Direct raman spectroscopic measurements of biological nitrogen fixation under natural conditions: An analytical approach for studying nitrogenase activity." Analytical Chemistry 89.2 (2017): 1117-1122.

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