Nitrogen Balance of a Floodplain Forest of the Amazon River: The Role of Nitrogen Fixation

In any agricultural system based on legumes, nitrogen balance should take into account the flow of NÂ 2 by legume species. In this flow, the amount of N2 fixed by legumes is considered a reserve amount of nitrogen which, through harvesting, is removed from the nitrogen balance. The aim of the present paper is to assess the amount of nitrogen fixed biologically (NFB) in some legume species sowed in association and of the share of this amount of NFB of the total amount of nitrogen from the productions obtained. Thus, in the fodder system made up of Italian ryegrass + red clover cultivated for two years, the amount of NFB in the first year was 60 kg/ha. If we relate the amount of NFB to the amount of nitrogen exported through the fodder biomass, we see that the share of NFB varies between 22 and 42%.

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Complex interactions in legume/cereal intercropping system: role of root exudates in root-to-root communication

10.1101/097584 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yinshan Jiao ◽

Entao Wang ◽

Wenfeng Chen ◽

Donald L. Smith

Keyword(s):

Nitrogen Fixation ◽

Root Exudates ◽

Faba Bean ◽

The Novel ◽

Practical Application ◽

Corn Root ◽

Complex Interactions ◽

Root Interactions ◽

Ecological Principles

Dear Editor,Legume/cereal intercropping systems have been regarded as the practical application of basic ecological principles such as diversity, competition and facilitation. In a recent PNAS paper, Li et al. (1) describe the novel finding that maize exudates promote faba bean nodulation and nitrogen fixation by upregulating genes involved in (iso)flavonoids synthesis (chalcone–flavanone isomerase) within faba bean, resulting in production of more genistein, a legume-to-rhizobia signal during establishment of the faba bean N2–fixing symbiosis. Although we salute the authors’ methodological efforts, there is another mechanism that could be responsible for the effect of corn root exudates on faba been nitrogen fixation observed in this article (1). The authors may misunderstand their data and the signalling role of maize exudates, thus got a defective model for the root interactions between faba bean and maize.

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Novel Reiterated Fnr-Type Proteins Control the Production of the Symbiotic Terminal Oxidase cbb3 in Rhizobium etli CFN42

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-20-10-1241 ◽

2007 ◽

Vol 20 (10) ◽

pp. 1241-1249 ◽

Cited By ~ 15

Author(s):

Manuel J. Granados-Baeza ◽

Nicolás Gómez-Hernández ◽

Yolanda Mora ◽

María J. Delgado ◽

David Romero ◽

...

Keyword(s):

Nitrogen Fixation ◽

Oxygen Affinity ◽

Structural Similarity ◽

Transcriptional Regulators ◽

Terminal Oxidase ◽

Nitrogen Fixing ◽

Rhizobium Etli ◽

High Oxygen Affinity ◽

Key Genes

Symbiotic nitrogen-fixing bacteria express a terminal oxidase with a high oxygen affinity, the cbb3-type oxidase encoded by the fixNOQP operon. Previously, we have shown that, in Rhizobium etli CFN42, the repeated fixNOQP operons (fixNOQPd and fixNOQPf) have a differential role in nitrogen fixation. Only the fixNOQPd operon is required for the establishment of an effective symbiosis; microaerobic induction of this operon is under the control of at least three transcriptional regulators, FixKf, FnrNd, and FnrNchr, belonging to the Crp/Fnr family. In this work, we describe two novel Crp/Fnr-type transcriptional regulators (StoRd and StoRf, symbiotic terminal oxidase regulators) that play differential roles in the control of key genes for nitrogen fixation. Mutations either in stoRd or stoRf enhance the microaerobic expression of both fixNOQP reiterations, increasing also the synthesis of the cbb3-type oxidase in nodules. Despite their structural similarity, a differential role of these genes was also revealed, since a mutation in stoRd but not in stoRf enhanced both the expression of fixKf and the nitrogen-fixing capacity of R. etli CFN42.

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