Different cytoplasmic calcium contents among three species of Characeae.

Abstract

Internodal cells of three species of Characeae, Nitella flexilis, Nitella axilliformis and Chara corallina, were analyzed for the contents of Ca(2+ )and Mg(2+) in the cytoplasm. To avoid contamination of Ca(2+) from the cell wall and vacuole, the vacuolar sap was replaced with a sorbitol solution containing Sr(2+) by the vacuolar perfusion method after the cell had been treated with Sr(2+). No significant difference in the cytoplasmic content of Mg(2+) was found among three species of Characeae, but significant differences in the cytoplasmic content of Ca(2+) were observed among them. The cytoplasmic Ca(2+) content of N. flexilis was 2.0 times that of N. axilliformis and 3.3 times that of C. corallina. The cytoplasmic drop was furthermore separated into two fractions: a chloroplast-free fraction and a chloroplast fraction. In the chloroplast-free fraction the Ca(2+) content of N. flexilis was 2.3 times that of C. corallina and 2.0 times that of N. axilliformis, while the Mg(2+) content was the same among the three species. In the chloroplast fraction N. flexilis contained about seven times more Ca(2+) and about two times more Mg(2+) than C. corallina. The difference in the cytoplasmic Ca(2+ )content was discussed in relation to the difference in the capacity for the hydration-induced Ca(2+) release existing among the three species.