The Growth and Intracellular Ionic Composition of Dunaliella tertiolecta in Magnesium-Rich Media

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Dunaliella tertiolecta grew in a medium that contained MgSO_4 (MgSO_4 medium), while this alga did not grow at all in media that contained MgCl_2 Or Mg(NO_3)_2. The growth in the MgSO_4 medium was inhibited in comparison with that in media that contained sodium salts, such as NaCl, NaNO_3, and Na_2SO_4. The energy charge obtained from measurements of levels of adenine nucleotides by HPLC were almost constant in Na- and Mg-containing media (about 0.87), indicating that the failure of growth in MgCl_2 medium and Mg(NO_3)_2 medium was not directly related to changes in the energy metabolism. K^+ and Mg^<2+> were the dominant intracellular cat-ions not only in Na-containing media (Mg-media) but also in Mg-containing media (Mg-media). The intracellular concentration of Ca^<2+ >was lower in Mg-media (1.6 mM) than that in Na-media (6 mM). The concentrations of HPO_4<2-> in cells incubated in Mg-media were lower (less than 60 mM) than those in Na-media (greater than I 10 mM). By contrast, the intracellular concentration of SO_4<2-> was higher in a MgSO_4 medium (26 mM) than that in a Na_2SO_4 medium (4 mM) which, at least, compensated by 40% for the decrease in HPO_4^<2->. The ability to grow in a MgSO_4 medium may be related to the high intracellular concentration of SO_4^<2->.
日本植物生理学会の論文