Cells of the green microalgaHaematococcus pluvialiswere induced to accumulate the ketocarotenoid pigment, astaxanthin. This induction was achieved by the application of the following environmental conditions: light intensity (170μmol m~−2s−1), phosphate starvation and salt stress (NaCl 0.8). These conditions retarded cell growth as reflected by a decrease in cell division rate, but led to an increase in astaxanthin content per cell. Accumulation of astaxanthin required nitrogen and was associated with a change in the cell stage from biflagellate vegetative green cells to non-motile and large resting cells. It is suggested that environmental or nutritional stresses, which interfere with cell division, trigger the accumulation of astaxanthin. Indeed, when a specific inhibitor of cell division was applied, a massive accumulation of astaxanthin occu
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