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1977; KAPLAN and ARNTZEN 1982). The main difference seems to lie in the variability of diameter and the regularity of arrangement of the stacked membrane regions. In Chlamydomonas there appears to be only a limited amount of regular arrangement; the thylakoids come together and move apart in an irregular manner. The thylakoids of Nitella (Characeae), on the other hand, often display an organization similar to higher plants with aligned stacks of thylakoids forming grana that are interconnected through typical, single stroma thylakoids.

Also indicated is a quinone electron transport cycle, or Q cycle, which causes the translocation of one additional proton for every two electrons passing through the linear electron transport chain. Protons deposited within the thylakoid lumen exit through the proton-translocating CF 0 -CF 1 A TP synthetase complex. Light-harvesting pigment-protein complexes (LHC) serve both photosystems; these preferentially associate with either PSI or PS II and are designated LHC I or LHC II, respectively. One population of the LHC II is mobile and can serve either PSI or PS II by traveling laterally between the stroma lamellae (enriched in PSI centers) and grana stacks (enriched in PS II).

MILLER and HoLT 1977), phosphorous starvation (STEVENS et al. 1981 b), and iron starvation (HARDIE et al. 1983). , BISALPUTRA 1974) have claimed that the thylakoids of cyanobacteria can be physically continuous with the cytoplasmic membrane, as is the case for nonoxygenic purple bacteria (see SPRAGUE and VARGA, Chap. 1, this VoL). A. STAEHELIN: Fig. 13. Negatively stained, isolated phycobilisomes (a) and phycobilisome cores (b) from wild-type Synechocystis 6701 (cyanobacterium). The core consists of a triangular array of circular complexes to which rods of stacked disc elements are attached on one side.