Microsecond delayed fluorescence of photosystem II of photosynthesis in various algae: emission spectra and uphill energy transfer

Abstract

In 195 1 Strehler and Arnold [l] discovered delayed fluorescence (for sake of simplicity we use in the following the term luminescence) of chlorophyll in the green alga Chlorella pyrenoidosa. The emission spectrum of the luminescence was found to be similar to that of (prompt) chlorophyll fluorescence of this alga [2].The hypothesis given in [2] that luminescence is caused by the reversal of photosynthetic reactions is generally accepted and for a recent review of this so-called ‘recombination’-hypothesis we refer to [3]. So far relatively few emission spectra of luminescence have been published. As far as we know spectra of luminescence components with decay times shorter than 100 /JS have not been published. We will present spectra with decay kinetics down to 0.2 /.Ls. Very recently Van Best and Duysens [4] reported a luminescence component in Cklorella vulgaris with a lifetime of -0.8 ~.ts. This luminescence seems to originate from reaction centers illuminated in the ‘closed’ state P680Q-, where P680 is the reduced primary donor and Othe reduced acceptor of Photosystem II (PS II). The emission spectrum of this luminescence component has been measured in addition to the luminescence spectra of components with lifetimes of 20 and 30 ,us in the state P680Q in the absence and presence of hydroxylamine. In the Photosystem I (PS I) lacking mutant Fl5 of Chlamydomonas reinhardtii, ps luminescence was present too and we have measured the spectrum. The accessory pigments of blue-green and red algae, phycocyanins and allophycocyanins are contained in particles (phycobilisomes) outside the membrane. Chlorophyll a and the reaction center are