Carbonic anhydrase in Ranunculus penicillatus spp. pseudofluitans: activity, location and implications for carbon assimilation |
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Authors: | J. R. NEWMAN J. A. RAVEN |
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Affiliation: | Department of Biological Sciences, University of Dundee, Dundee DDI 4HN, UK |
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Abstract: | Levels of carbonic anhydrase activity were determined on a total (60 EUmg?1 protein), external (7.36 EU), internal (50.14 EU) and protoplast (15.63 EU) basis for Ranunculus penicillatus (Dumort.) Bab ssp. pseudofluitans (Syme) S. Webster, a freshwater aquatic macrophyte, by conventional electrometric methods. The site of activity of ‘external’ carbonic anhydrase (CA) has been visualized using 5-Dimethylaminonapthalene-1- sulphonamide (DNSA)-CA fluorescent complex formation, and is postulated to be closely associated with the epidermal cell wall. The photosynthetic rate of R. penicillatus ssp. pseudofluitans at pH 9.0 is in excess of the uncatalysed rate of production of CO2 from HCO?3, and this plant is therefore using HCO?3 for photosynthesis. The possible contribution of CA activity to inorganic carbon assimilation, and specifically to transport of HCO?3, in submerged aquatic plants is discussed. |
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Keywords: | Ranunculus penicillatus ssp. pseudofluitans Ranunculuaceae Water Crowfoot carbonic anhydrase carbon assimilation |
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