Arrested development in Fucus spiralis (Phaeophyceae) germlings exposed tocopper

Exposure of Fucus spiralis germlings to precise copper concentrations (0 to 844 nM Cu2+) in chemically defined medium demonstrated a relationship betw een urltrastructural changes and growth retardation with increasing copper concentration. Electron-translucent vesicles, present in ova, which normall y disappear after fertilization, accumulated in germlings exposed to Cu2+ a bove 10.6 nM, suggesting that copper may inhibit a metabolic pathway involv ed in cell wall formation which is initiated by fertilization No membrane d amage was observed during the exposure period. During a post-exposure perio d in copper-free medium, recovery occurred (rhizoid extension, apical hair formation) in germlings previously exposed to concentrations below 106 nM C u2+ and electron-translucent vesicles became granular and disappeared. It i s proposed that the electron-translucent vesicles contain a cell wall precu rsor and that copper inhibits its incorporation into the cell wall, prevent ing growth and development of the zygote.