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

Thermoluminescence (TL) was used to study charge separation and stabilization in different states of photosystem II (PS II) in heterotrophic cells of the green alga Chlorella kessleri Ys/Sc. Under various excitation 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 flashes in the presence or absence of diuron revealed states of charge recombination involving the water oxidizing system: S(3)Q(A)(-) (-5 degrees 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 corresponding to the TL band at 45 degrees C is accumulated with a very low quantum yield and probably corresponds to a fraction of functionally inactive PS II complexes without a formed Mn complex of the water oxidizing 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 independent 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 centers.