Ion Composition of the Chara Internode

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Ion compositions of the cytoplasm and the vacuole of Chara australis were analyzed according to Kishimoto and Tazawa (1964) and Kiyosawa (1979a). The ions in the cytoplasm and the vacuole analyzed were K^+, Na^+, Ca^<2+>, Mg^<2+>, Cl^-, NO_3^- and H_2PO_4^-. Assuming that the volume of the cytoplasm V_p is 10% of that of the whole cell V, the concentrations of K^+, Na^+ Ca^<2+>, Mg^<2+>, Cl^-, NO_3^- and H_2PO_4^- in the cytoplasm averaged 70, 15, 13, 4.6, 31, 2.2 and 16 mM, respectively. If the volume of the cytoplasm was assumed to be 5% of that of the whole cell, their averaged concentrations were 139, 31, 25, 9.2, 62, 4.4 and 33 mM, respectively. The averaged ion compositions of the cell sap were K^+, 111; Na^+, 47; Ca^<2+>, 4.4; Mg^<2+>, 8.9; Cl^-, 91; NO_3^-, 3.3 and H_2PO_4^-, 6.0 mM. These values, taking the concentrations and the charges of the protein (Kiyosawa 1979b) and amino acids (Sakano and Tazawa 1984) into account and assuming the presence of some uni- or oligovalent anions and/or small nonelectrolyte molecules, could explain fairly well both the electroneutrality and the osmotic pressure of the cell, except when V_p/V=5%.
日本植物生理学会の論文