EFFECT OF NITROGEN OR PHOSPHORUS STARVATION ON PIGMENT COMPOSITION OFCULTURED HETEROCAPSA SP

The effect of nitrogen (N) and phosphorus (P) depletion on the cell vo lume and pigment composition of the marine dinoflagellate Heterocapsa sp. was studied. Cell size increased under both N or P starvation. but the change was faster when P was limiting. Quantitatively, N deficien cy resulted in greater pigment loss than did P deficiency, thereby cor roborating the relationship between pigment synthesis and N metabolism . It is suggested that the synthesis of pigments is primarily stopped at a transcriptional level (from DNA to RNA) under P limitation and at a translational level (from RNA to proteins) under N limitation. Almo st all pigments underwent a parallel decrease during the stationary ph ase and no clear changes in pigment ratios were found. As an exception , a pigment identified as diatoxanthin accumulated in the algae when c ell growth ceased. This occurred regardless of the growth-limiting nut rient and became more pronounced as cell deterioration progressed.