Journal Article

The Influence of Anoxia on Plants of Saline Habitats with Special Reference to the Sulphur Cycle

John A. Raven and Charles M. Scrimgeour

in Annals of Botany

Published on behalf of Annals of Botany Company

Volume 79, issue suppl_1, pages 79-86
Published in print January 1997 | ISSN: 0305-7364
Published online January 1997 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/oxfordjournals.aob.a010309
The Influence of Anoxia on Plants of Saline Habitats with Special Reference to the Sulphur Cycle

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Plants of saline habitats can encounter anoxic conditions to extents which vary with habitat and life form. Rhizophytes (with roots or rhizoids in a sediment) routinely have anoxia or hypoxia in their roots, rhizoids and rhizomes. Haptophytes (attached to large particles of substrate) and planophytes (unattached) are generally less prone to anoxia or hypoxia, exceptions being ice-encased polar haptophytes and estuarine and muddy shore macroscopic planophytes (pleustophytes) which can become hypoxic or anoxic as a result of burial in sediment or under new growth.

A major difference between anoxia in low-salinity habitats and anoxia in saline habitats is the presence of high sulphate concentrations in most saline habitats including seawater. Use of sulphate as electron acceptor in microbial oxidation or organic carbon produces sulphide, with relatively less production of methane than in anoxic habitats with lower sulphate concentrations. In addition to its role as a toxin. 34S/32S natural abundance data show that 34S-depleted sulphide is directly or indirectly used as a sulphur source for roots and rhizomes of seagrasses and for the whole organism of emergent salt marsh herbs and mangroves. Granted the presence of hydrogen sulphide in the rhizosphere, its entry by lipid-solution permeation of the plasmalemma is inevitable. The balance of evidence favours the entry of hydrogen sulphide rather than the oxidation of 34S-depleted sulphide to 34S-depleted sulphate in an aerobic rhizosphere with subsequent entry of sulphate.

Keywords: Anoxia; haptophytes; hydrogen sulphide; mangroves; planophytes; rhizophytes; salt marshes; seagrasses; seaweeds; sulphate

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Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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