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Effects of various ionic conditions on the development of the cellular slime molds D. discoideum and D. mucoroides were studied. A certain concentration of lithium ions (7 mM) promoted differentiation of the stalk cells and conversely inhibited formation of the spores. The presence of calcium and magnesium ions was needed for Li to manifest its specific effect. A high concentration of Ca (100-120 mM) also facilitated differentiation of the stalk cells. On the other hand, fluoride ions stimulated considerable formation of spores at 15 mM. In the absence of divalent cations, sodium ions inhibited morphogenesis and cell differentiation proportionately with its concentration, and complete inhibition was obtained at 20 mM. The inhibitory effect of Na was nullified by addition of small amounts of Ca. Possible mechanisms by which these ions exert their influences on development of this organism were discussed.
Yasuo Maeda (Thu,) studied this question.