Effect of inhibitors of carbonic anhydrase activity on photosynthesis in the red alga Soliera filiformis (Gigartinales: Rhodophyta) |
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Authors: | J. L. Gómez-Pinchetti Z. Ramazanov G. García-Reina |
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Affiliation: | (1) Laboratorio de Biotecnología Vegetal Marina, Universidad de Las Palmas de Gran Canaria, Box 550, Las Palmas, Islas Canarias, Spain;(2) Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 276 Moscow, Russia;(3) Present address: Departamento de Bioquímica, Facultad de Ciencias, Universidad de Córdoba, E-14071 Cordoba, Spain |
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Abstract: | The effect of light intensity, pH and carbonic anhydrase (CA) inhibitors on photosynthesis of the red marine macroalgae Solieria filiformis (Kützing) Gabrielson, collected from Taliarte (Gran Canaria, Canary Islands) in 1991, has been investigated. Plants taken from the sea (wild phenotype) developed spherical morphology (ball phenotype) after 2 mo culture in aerated tanks. The photosynthetic oxygen evolution in the wild phenotype was saturated at 100 mol photons m-2s-1, while the ball phenotype displayed saturation at 200 mol photons m-2s-1. The inhibitors of total CA activity (6-ethoxizolamide) and extracellular CA activity (dextran-bound sulfonamide) inhibited photosynthesis at pH 8.2, to 90 and 50% respectively, in both phenotypes. No inhibition of the photosynthetic oxygen evolution was detected at pH 6.5. CA activity was associated with both supernatant and pellet fractions of crude extracts of S. filiformis. The rate of alkalization of the medium by the algae was dependent on light intensity. We suggest that carbon dioxide is the general form of inorganic carbon transported across the plasmamembrane in S. filiformis. HCO3 transport into the cell takes place simultaneously by an indirect mechanism (dehydration to CO2 catalyzed by CAext) and by direct uptake. Extracellular (CAext) and intracellular (CAint) CAs are involved in the mechanisms of inorganic carbon assimilation by S. filiformis. |
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