[Uptake of labeled zinc by Chlorella containing different amounts of zinc].

Chlorella fusca was grown asynchronously for 2 weeks in media with different Zn concentrations up to 10(-3) M. Growth was optimal at 10(-5) M Zn. The Zn contents of the algae were followed by activation analysis. They increased with increasing Zn concentration in the media, and, except with the lowest Zn concentrations, with time. Further, the uptake of labelled Zn (65Zn) from 5 . 10(-6) M solution by cells of known Zn content was measured at 30 degrees C during one day in minimum and optimum conditions (dark/nitrogen or light/air, respectively). The rate of uptake showed a maximum with algae grown in a medium with 10(-5) M Zn. However, algae exposed to a lethal Zn concentration (10(-3) M) also absorbed much Zn; this anomalous uptake is ascribed to a breakdown of the cell membrane as a permeability barrier.