Journal Article

Cellular basis of growth suppression by submergence in azuki bean epicotyls

Kentaro Ooume, Yuki Inoue, Kouichi Soga, Kazuyuki Wakabayashi, Shuhei Fujii, Ryoichi Yamamoto and Takayuki Hoson

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 103, issue 2, pages 325-332
Published in print January 2009 | ISSN: 0305-7364
Published online October 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn198
Cellular basis of growth suppression by submergence in azuki bean epicotyls

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

Complete submergence severely reduces growth rate and productivity of terrestrial plants, but much remains to be elucidated regarding the mechanisms involved. The aim of this study was to clarify the cellular basis of growth suppression by submergence in stems.

Methods

The effects of submergence on the viscoelastic extensibility of the cell wall and the cellular osmotic concentration were studied in azuki bean epicotyls. Modifications by submergence to chemical properties of the cell wall; levels of osmotic solutes and their translocation from the seed to epicotyls; and apoplastic pH and levels of ATP and ethanol were also examined. These cellular events underwater were compared in etiolated and in light-grown seedlings.

Key Results

Under submergence, the osmotic concentration of the cell sap was substantially decreased via decreased concentrations of organic compounds including sugars and amino acids. In contrast, the viscoelastic extensibility of the cell wall was kept high. Submergence also decreased ATP and increased the pH of the apoplastic solution. Alcoholic fermentation was stimulated underwater, but the resulting accumulated ethanol was not directly involved in growth suppression. Light partially relieved the inhibitory effects of submergence on growth, osmoregulation and sugar translocation.

Conclusions

A decrease in the levels of osmotic solutes is a main cause of underwater growth suppression in azuki bean epicotyls. This may be brought about by suppression of solute uptake via breakdown of the H+ gradient across the plasma membrane due to a decrease in ATP. The involvement of cell wall properties in underwater growth suppression remains to be fully elucidated.

Keywords: Apoplastic pH; cell wall extensibility; growth suppression; osmoregulation; osmotic concentration; submergence; sugar translocation; Vigna angularis

Journal Article.  4929 words.  Illustrated.

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

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