Journal Article

Ion and Oxygen Fluxes in the Unicellular Alga <i>Eremosphaera viridis</i>

Roger R. Lew

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 11, pages 1889-1899
Published in print November 2010 | ISSN: 0032-0781
Published online October 2010 | e-ISSN: 1471-9053 | DOI:
Ion and Oxygen Fluxes in the Unicellular Alga Eremosphaera viridis

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry


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Plasma membrane fluxes of the large unicellular model algal cell Eremosphaera viridis (De Bary) were measured under various light regimes to explore the role of plasma membrane fluxes during photosynthesis and high light-induced chloroplast translocation. Plasma membrane fluxes were measured directly and non-invasively with self-referencing ion-selective (H+, Ca2+, K+ and Cl) potentiometric microelectrodes and oxygen amperometric microelectrodes. At light irradiances high enough to induce chloroplast migration from the cell periphery to its center, oxygen evolution declined to respiratory net O2 uptake prior to any significant chloroplast translocation, while net K+ and Cl influx increased during the decline in photosynthetic activity (and the membrane potential depolarized). The results suggest that chloroplast translocation is not the cause of the cessation of O2 evolution at high irradiance. Rather, the chloroplast translocation may play a protective role: shielding the centrally located nucleus from damaging light intensities. At both high and low light intensities (similar to ambient growth conditions), there was a strong inverse correlation between H+ net fluxes and respiratory and photosynthetic net O2 fluxes. A similar inverse relationship was also observed for Ca2+ net fluxes, but only at higher light intensities. The net H+ fluxes are small relative to the buffering capacity of the cell, but are clearly related to both photosynthetic and respiratory activity.

Keywords: Chloroplast translocation; Eremosphaera viridis; Ion fluxes; Oxygen fluxes; Photosynthesis; Unicellular alga

Journal Article.  6731 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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