Iron sulfide formation on root surfaces controlled by the life cycle of wild rice (Zizania palustris)

Sophia LaFond-Hudson, Nate Johnson, John Pastor, Brad Dewey

Research output: Contribution to journalArticle

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Abstract

Iron sulfide plaques have been observed on roots of wild rice (Zizania palustris) and other wetland plants grown in sulfur-impacted freshwater ecosystems, but the mechanism of their formation and ramifications for plants have not been investigated. We exposed a model annual wetland plant, Zizania palustris, to elevated sulfate concentrations (3.1 mM) and quantified the development of iron oxide and iron sulfide precipitates on root surfaces throughout the plant life cycle. During the onset of seed production, root surfaces amended with sulfate transitioned within 1 week from iron (hydr)oxide plaques to iron sulfide plaques. During the same week, Fe(III) decreased on roots of plants not amended with sulfate but FeS did not accumulate. Prior to FeS accumulation, sulfate-amended plants had taken up the same amount of N as unamended plants. After FeS accumulation, total plant nitrogen did not increase further on sulfate-amended plants, indicating a cessation in nitrogen uptake, whereas total plant N continued to increase in unamended plants. Sulfate-amended plants produced fewer and lighter seeds with less nitrogen than unamended plants. FeS precipitation on roots may be associated with elevated sulfide and inhibited nitrogen uptake before the end of the plant’s life cycle, thus affecting the populations of this annual aquatic plant. We propose a mechanism by which a physiologically-induced decline in radial oxygen loss near the end of a plant’s life cycle initiates a precipitous decline in redox potential at the root surface and in adjacent porewater, initiating accumulation of iron sulfide plaques. These plaques could be an important locus for iron sulfide accumulation in wetland sediments.

Original languageEnglish (US)
Pages (from-to)95-106
Number of pages12
JournalBiogeochemistry
Volume141
Issue number1
DOIs
StatePublished - Oct 1 2018

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iron sulfide
Sulfides
Sulfates
Life cycle
rice
life cycle
Iron
Wetlands
Nitrogen
sulfate
Seed
nitrogen
wetland
Sulfur
Ecosystems
iron oxide
Precipitates
Sediments
Oxygen
freshwater ecosystem

Keywords

  • Electron accepting buffer
  • Iron–sulfur cycling
  • Radial oxygen loss
  • Root plaques
  • Zizania palustris

Cite this

Iron sulfide formation on root surfaces controlled by the life cycle of wild rice (Zizania palustris). / LaFond-Hudson, Sophia; Johnson, Nate; Pastor, John; Dewey, Brad.

In: Biogeochemistry, Vol. 141, No. 1, 01.10.2018, p. 95-106.

Research output: Contribution to journalArticle

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