CALCIFICATION RATE IN EMILIANIA-HUXLEYI LOHMANN IN RESPONSE TO LIGHT, NITRATE AND AVAILABILITY OF INORGANIC CARBON

被引:85
作者
NIMER, NA
MERRETT, MJ
机构
[1] School of Biological Sciences, University College of Swansea, Swansea, SA2 8PP, Singleton Park
关键词
CALCIFICATION; LIGHT; NITROGEN; INORGANIC CARBON; EMILIANI-HUXLEYI;
D O I
10.1111/j.1469-8137.1993.tb03776.x
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
The relationship between photosynthesis and calcification was investigated in a high-calcifying strain of Emiliania huxleyi. At pH 8.3 and a photon flux density of 50 mumol m-2 s-1 calcification and photosynthetic (CO2)-C-14 fixation were carbon saturated at 1 mm DIC (dissolved inorganic carbon) but at a photon flux density of 300 mumol m-2 s-1 calcification and photosynthetic (CO2)-C-14 fixation were not saturated at the DIC concentration of sea-water, 2 mm. When HCO3- provides the bulk of inorganic carbon the stoichiometry between photosynthetic (CO2)-C-14 fixation and calcification was 1:1. In the high-calcifying strain of E. huxleyi the stoichiometry between photosynthetic (CO2)-C-14 fixation and O2 evolution was 2:1 but in a low calcifying strain the stoichiometry was 1:1. High nitrate concentrations, i.e. 1000 muM were required to inhibit calcification. The optimum pH for calcification and photosynthetic (CO2)-C-14 fixation was 7.8. From the results a model is proposed in which a molecule of HCO3- is the precursor of calcite in the coccolith vesicle with the extrusion of H+ into the cytosol, while another HCO3- provides CO2 in the chloroplast with the extrusion of OH-. The interaction of these processes maintains cytoplasmic pH near neutrality.
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页码:673 / 677
页数:5
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