RELATIONSHIP BETWEEN QUENCHING OF MAXIMUM AND DARK-LEVEL CHLOROPHYLL FLUORESCENCE IN-VIVO - DEPENDENCE ON PHOTOSYSTEM-II ANTENNA SIZE

The effects of nonphotochemical quenching were quantified separately a pplying the Stern-Volmer formalism for dark level (SV0) and maximum ch lorophyll fluorescence yield (SVN) in barley leaves comprising a step- wise altered Photosystem II (PS II) antenna size. Proportions of overa ll SVN can be attributed to distinct sites of the photosynthetic appar atus: (i) the bulk light-harvesting complex of PS II (LHC II), (ii) th e inner LHC II antenna, and (iii) the reaction center/core complex of PS II. The fraction of SVN which exerts an effect on SV0 appeared to a rise almost exclusively from the inner LHC II antenna. A strong linear correlation between SV0 and violaxanthin de-epoxidation points to an intrinsic relationship of both. The results are in line with the natio n of a regulatory function of the inner LHC II antenna, thus controlli ng excitation energy delivery from the bulk LHCII to the PS II-core co mplex.