The Biological Bulletin, Vol 180, Issue 1 185-195, Copyright © 1991 by Marine Biological Laboratory

PHYSIOLOGY

Calcium-Proton Exchange During Algal Calcification

T. A. McConnaughey and R. H. Falk
Marine Biological Laboratory, Woods Hole, Massachusetts 02543

Extracellular calcification by the giant celled alga Chara corallina may involve active Ca2+ extrusion from the cell in exchange for protons. The following evidence is presented: CaCO3 incrustations accrete largely along the inside, facing the cell, as revealed by X-ray microanalysis using Sr2+ and Mn2+ as tracers for new mineralization. Inward proton currents are inhibited by the Ca2+ transport antagonists Gd3+ and La3+. Low Ca2+ concentrations inhibit pH banding and photosynthesis, and solutions of low Ca2+ activity support more photosynthesis in the presence of additional buffered calcium. The ratio of calcification to photosynthesis in moderately alkaline solutions containing sufficient calcium remains stable at about 1.0 independent of solution Ca2+ concentration. Ion specific microelectrodes placed close to the calcified surface sometimes detect increases in Ca2+ activity coincident with decreases in proton activity. As the pCa of solution increases, the maximum pH observed at the alkaline surface increases, as does the maximum solution pH which supports electrochemical currents by the cell. Combinations of extracellular pH and pCa approach the calculated thermodynamic limits for ATP driven 2H+/Ca2+ exchange against the cytosol.

This article has been cited by other articles:

				F. t. Hoopen, T. A. Cuin, P. Pedas, J. N. Hegelund, S. Shabala, J. K. Schjoerring, and T. P. Jahn Competition between uptake of ammonium and potassium in barley and Arabidopsis roots: molecular mechanisms and physiological consequences J. Exp. Bot., May 1, 2010; 61(9): 2303 - 2315. [Abstract] [Full Text] [PDF]

				J. J. DONOVAN ON THE MEASUREMENT OF REACTIVE MASS FLUXES IN EVAPORATIVE GROUNDWATER-SOURCE LAKES Sedimentology and Geochemistry of Modern and Ancient Saline Lakes, February 1, 2010; 33 - 50. [Abstract] [PDF]

				I. Sethmann, A. Putnis, O. Grassmann, and P. Lobmann Observation of nano-clustered calcite growth via a transient phase mediated by organic polyanions: A close match for biomineralization American Mineralogist, July 1, 2005; 90(7): 1213 - 1217. [Abstract] [Full Text] [PDF]

				O. Babourina, K. Voltchanskii, and I. Newman Ion flux interaction with cytoplasmic streaming in branchlets of Chara australis J. Exp. Bot., December 1, 2004; 55(408): 2505 - 2512. [Abstract] [Full Text] [PDF]

				A. L. Cohen, A. L. Cohen, and T. A. McConnaughey Geochemical Perspectives on Coral Mineralization Reviews in Mineralogy and Geochemistry, January 1, 2003; 54(1): 151 - 187. [Full Text] [PDF]

				P. Furla, S. Benazet-Tambutte, J. Jaubert, and D. Allemand Functional polarity of the tentacle of the sea anemone Anemonia viridis: role in inorganic carbon acquisition Am J Physiol Regulatory Integrative Comp Physiol, February 1, 1998; 274(2): R303 - R310. [Abstract] [Full Text] [PDF]