. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ALGAL CALCIFICATION 189 CALCIFICATION TO PHOTOSYNTHESIS RATIO 15KV 30UM Figure 3. Distributions of Ca (yellow), Sr (blue), and Mn (red) in an extracellular CaCO3 deposit, visualized by X-ray mapping of a frozen. hydrated cell exposed to Sr:+ and Mn:+ after first accumulating significant CaCO3. Sr and Mn accumulations presumably consist of di- valent metal carbonates and MnO2, the latter inferred from its dark color. Manganese oxidation, Mn2+ + H2O + '/2O2 = MnO2 + 2H+, is favored in the alkaline, oxygen- rich environm
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ALGAL CALCIFICATION 189 CALCIFICATION TO PHOTOSYNTHESIS RATIO 15KV 30UM Figure 3. Distributions of Ca (yellow), Sr (blue), and Mn (red) in an extracellular CaCO3 deposit, visualized by X-ray mapping of a frozen. hydrated cell exposed to Sr:+ and Mn:+ after first accumulating significant CaCO3. Sr and Mn accumulations presumably consist of di- valent metal carbonates and MnO2, the latter inferred from its dark color. Manganese oxidation, Mn2+ + H2O + '/2O2 = MnO2 + 2H+, is favored in the alkaline, oxygen- rich environment of the plant surface. More or less pure Mn accumulations, based on relative X-ray counts for 120. 4 6 ENERGY (KeV) 10 Figure 4. X-ray spectra taken at points "A" and "B" of cell shown in Figure 2. Spectra correspond to materials deposited after (A) and before (B) addition of Sr2+ and Mn2+ to the medium. X-ray counts are scaled relative to the Ca peak (100%); spectrum A has been shifted up- wards by 20% for clarity. 1 0 - D D ,' *-, i a'n ' ° 10 - ° ~~^j ! PHOTOSYNTHESIS f : i 1 05 1 /' 0 - -j -4 Q_ DIC = 2mM pH - 8 o • CALCIUM (mM) 1234 J 10 20 30 CALCIUM (mM) 40 50 Figure 5. Ratio of calcification to photosynthesis near pH 8 as a function of Ca2* concentration. Inset: inhibition of photosynthesis by low Ca2+ concentrations. Error bars: 1 Mn, Sr, and Ca, sometimes occur beneath CaCO, in- crustations, even when the incubating medium contains considerably more Ca2+ and Sr2+. Mn enrichment may reflect kinetics of transport or precipitation, and was probably assisted by oxidation of Mn:+ to Mn4+, thus producing a less soluble, non-transportable cation. Indentations of the cell and apparent duplications of the cell wall sometimes occur underneath CaCO3 incrus- tations (Fig. 2). Non-calcified regions of the cell lack such features. Calcification within the cell wall may force the plasma membrane inward, followed by the secretion of a new wall. Thi
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
