Measurements of Ion Concentrations inDunaliella parvaSubjected to Hypertonic Shock

Cells of Dunaliella parva, a green halotolerant alga, were equilibratedin 0.5 M NaCl (the same concentration as in the growth medium).The time – course of changes in K⁺, Na⁺, Cl^–, andpellet volume were followed after a hypertonic shock causedby increasing the outside NaCl concentration to 1 M. The cellsresponded initially by shrinking; they returned to their originalvolume in the course of the next 2–3 h. At the time ofthe hypertonic shock there were rapid influxes of Na⁺ and Cl^–which took about 30 min for completion. Thereafter, there wereprogressive losses of Na⁺ and Cl^–; these losses were temperature-dependentand presumably activated by metabolic energy. Cell K⁺ remainedconstant throughout.