CALCIFICATION AND CATION SORPTION OF CLADOPHOHA GLOMERATA (CHLOROPHYTA)1, 2 |
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Authors: | C. Steven Sikes |
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Abstract: | Clacium sorption by Cladophora glomerata (L.) Kutz grown in continuous-flow culture increased substantially as the alga aged (12.3–160 mg Calg dry wt). This reflected increased pectin layered in thickening cell walls followed by deposition of CaCO3 around cells. The high levels of pectin (up to 23% of dry wt) may account for the plant's reported high affinity for cations. The onset of carbonate deposition coincided with the appearance of carbonabic anhydrase activity in cells. This suggests that carbonate deposition mey be a funtion of bicarbonate use as a source of CO2 for photosynthesis. Calcium uptake appears to occur by active transport in that it exhibited saturation kinetics, occurred against a concentration gradient, depended on light, and was nearly abolished by treatments that allow diffusion. Although strontium competed for Ca for binding sites of pectin, it did not inhibit intermal transport of Ca. Consequently, the proposed carrier may be specific for Ca. |
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Keywords: | calcification calcium transport carbonic anhydrase Cladophora pectin radionuclides |
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