Fluorescence and Absorption Changes in Chlorella Exposed to Strong Light: The Red Band.

The reversible decrease in the apparent intensity of the main red absorption band of chlorophyll a at 680 mnu upon strong illumination of Chlorella cells, described by Coleman and Rabinowitch in 1957, is shown, by a polarization method, to be due to an increase in the fluorescence yield. True absorption changes are observed at 657 mnu (positive) and 648 mnu (negative).