Development and Repair of Photosystem II Activity in Normal and Chloramphenicol-treated Euglena gracilis Cells

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Abstract
Photosystem II activity, development and organization were studied in membranes from dark-adpated E. gracilis Klebs var. Z Pringsheim cells during a modulated greening processing of light-dark-light cycles. The results obtained from measurements of overlapping partial photosystem II (PSII) reactions (fluorescence induction parameters, quantum yield, flash yield and maximal rate of H2O .fwdarw. 2,6-dichlorophenolindophenol [DCIP] and 1,5-diphenylcarbazide [DPC] .fwdarw. DCIP reactions) during these cycles indicate the formation of active PSII units in the dark. The necessity for proteins from the chloroplast translational machinery for this formation is evidenced by the inhibition of synthesis of the PSII units in chloramphenicol-treated cells. The effect of this drug, both during the dark and 2nd light periods, was summarized as disruption of the electron transfer connection to the plastoquinone pool, or decrease in the pool size; loss of excitation energy transfer efficiency in the 2nd light period; impairment of the O2 evolution apparatus, as shown by comparison of the efficiency of DCP and H2O as electron donors. These conclusions are based on the use of a previously developed method of measurement and analysis of data.