Biosynthetic and Ultrastructural Events Associated with the Selective Formation of System II Reaction Centers in Euglena Mature Chloroplasts

Abstract

Functional, biochemical and ultrastructural studies of photosynthetic membranes (Miller et al, 1976; Armond et al, 1977; Dubertret and Lefort-Tran, 1978; Miller and Cushman, 1979; Wollman et a1,198O) have led to a model where 160 Â EFs particles in cryofractured thylakoids would correspond to the morphological expression of photosystem II light-harvesting and trapping systems. However, the mean distance between EFs particles appears to be too large to account for the observed energy transfers between system II units which then could occur 1) either between EFs particles of adjacent membranes brought in contact in stacked areas (Dubertret and Lefort-Tran, 1982) 2) or between EFs particles of the same membrane, through exciton-conducting pigments which could be located on the complementary PFS face (Wollman et al., 1980). We present here results obtained on a modified greening system, which support this last hypothesis.