THE RELATION BETWEEN THE MINOR CHLOROPHYLL SPECTRAL FORMS AND FLUORESCENCE QUENCHING IN AGGREGATED LIGHT-HARVESTING CHLOROPHYLL A B COMPLEX-II/

The hypothesis that fluorescence quenching in aggregated light harvest ing chlorophyll a/b protein complex II is associated with the formatio n of minor spectral forms absorbing near 655 nm and between 680 nm-690 nm is examined. Using an homogeneous LHCII preparation, steady-state absorption changes measured at room temperature are quantitatively com pared with the associated steady state fluorescence changes by means o f the Stepanov relation. It is demonstrated that upon LHCII aggregatio n, the relative fluorescence yield is constant for chlorophyll forms a bsorbing between 650 nm and 690 nm. This indicates that the minor chlo rophyll forms formed upon LHCII aggregation are not quenching species.