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. 1989 Sep;91(1):315–321. doi: 10.1104/pp.91.1.315

Effects of Gradual Increases in O2 Concentration on Nodule Activity in Soybean 1

Stephen Hunt 1, Bryan J King 1, David B Layzell 1
PMCID: PMC1061993  PMID: 16667018

Abstract

The objectives of this study were to determine whether attached nodules of soybean (Glycine max L. Merr.) could adjust to gradual increases in rhizosphere pO2 without nitrogenase inhibition and to determine whether the nitrogenase activity of the nodules is limited by pO2 under ambient conditions. A computer-controlled gas blending apparatus was used to produce linear increases (ramps) in pO2 around attached nodulated roots of soybean plants in an open gas exchange system. Nitrogenase activity (H2 production in N2:O2 and Ar:O2) and respiration (CO2 evolution) were monitored continuously as pO2 was ramped from 20 to 30 kilopascals over periods of 0, 5, 10, 15, and 30 minutes. The 0, 5, and 10 minute ramps caused inhibitions of nitrogenase and respiration rates followed by recoveries of these rates to their initial values within 30 minutes. Distinct oscillations in nitrogenase activity and respiration were observed during the recovery period, and the possible basis for these oscillations is discussed. The 15 and 30 minute ramps did not inhibit nitrogenase activity, suggesting that such inhibition is not a factor in the regulation of nodule diffusion resistance. During the 30 minute ramp, a stimulation of nitrogenase activity was observed, indicating that an O2-based limitation to nitrogenase activity occurs in soybean nodules under ambient conditions.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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