Summary
The objectives of this investigation were to determine the effects of oxygen partial pressure (pO2) and combined nitrogen (NH +4 ) on rates of acetylene reduction (AR) associated with roots of intact corn, sorghum, and pearl millet plants. Soil-grown plants were carefully removed from soil and incubated hydroponically with the root system enclosed in a plastic cylinder; the tops were left exposed to ambient conditions. Oxygen concentrations around the root systems were controlled by sparging the nutrient solution with known quantities of O2 in N2. Ammonium nitrogen was added to the nutrient solution following establishment of AR rates to determine its effect on rates of N2-fixation (AR). Substantial AR rates (0.1–1.5 μmol C2H4 g dry wt−1 h−1) were associated with roots exposed to 0–2% O2 (v/v) (0.0–2.02 kPa) in N2 following at 12–24 h period of exposure to the reduced oxygen tension. Root systems exposed to air failed to demonstrate AR while those exposed to 100% N2 showed lower activity than those at reduced pO2 values. Addition of NH +4 (10–20 μg N ml−1 of nutrient solution) reduced AR by 75–90% within 24 h after addition. Oxygen uptake by roots exposed to low pO2 was substantially reduced.
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Zuberer, D.A., Alexander, D.B. Effects of oxygen partial pressure and combined nitrogen on N2-fixation (C2H2) associated withZea mays and other gramineous species. Plant Soil 90, 47–58 (1986). https://doi.org/10.1007/BF02277386
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DOI: https://doi.org/10.1007/BF02277386