Chlorophyll fluorescence from single cells: interpretation of flow cytometric signals,” Limnol

The relationship between flow cytometric fluorescence signals and photosynthetic pigments was investigated in three species of marine eucaryotic phytoplankton, ThaZassiosiru weissflogii, Hy-menomonas carterae, and Amphidinium carteri. The species were grown over a range of light intensities to provide a spectrum of pigment compositions for the study. Both interspecific and intraspecific differences were observed. Variations among the species in fluorescence per unit of chlorophyll a (Chl a) could be explained by differences in the relative abundance of Chl a and accessory pigments. Amphidinium carteri had much greater fluorescence per unit of Chl a than the other two species and it had the highest Chl c: Chl a ratio. Fluorescence per unit of Chl a decreased as Chl a per cell increased in H. carterae and A. carteri, whereas it remained the same in T. weissflogii. We interpret these differences to have their origins in the “package ” effect on light absorption. This effect seems to be least evident in the diatom because cell size increased as Chl a per cell increased in low-light-grown cells. In H. carterae and A. carteri the opposite was true, such that the intracellular concentration of Chl a increased substantially in the low-light cells. Based on these data, we find that to interpret fluorescence signals among species, differences in th