THERMOLUMINESCENCE STUDY OF PHOTOSYSTEM-II IN A GREENING MUTANT OF CHLORELLA-KESSLERI .1. STRUCTURE-FUNCTIONAL PROPERTIES OF PHOTOSYSTEM-IICOMPLEXES IN GREEN CELLS

Thermoluminescence (TL) was used to study charge separation and stabil ization in different states of photosystem II (PS II) in heterotrophic cells of the green alga Chlorella kessleri Ys/Sc. Under various excit ation conditions, at least nine TL bonds were found, at -75, -30, -5, 12, 17, 22, 35, 45, and 55 degrees C. Illumination with short light fl ashes in the presence or absence of diuron revealed states of charge r ecombination involving the water oxidizing system: S(3)Q(A)(-) (-5 deg rees C), S(2)Q(A)(-) (12 degrees C), S(3)Q(B)(-) (17 degrees C), S(2)Q (B)(-) (22 degrees C), and S(2)Q(B)H (35 degrees C). The stare corresp onding to the TL band at 45 degrees C is accumulated with a very low q uantum yield and probably corresponds to a fraction of functionally in active PS II complexes without a formed Mn complex of the water oxidiz ing system. The TL curves of light saturation at 22 degrees C (S(2)Q(B )(-)) induced by a single flash are consistent with a model of indepen dent unicenter PS II units, whereas at 12 degrees C (S(2)Q(A)(-)) they are better described by the model of a multicenter (n > 4) domain of PS II subunits with energy transfer from closed to open reaction cente rs.