EFFECTS OF CHOLESTEROL AND BENZYL ALCOHOL ON FLUORESCENCE TRANSIENTS OF PEA THYLAKOIDS

Using the chlorophyll fluorescence induction and oxygen evolution meas urements we investigated the influence of alteration of the fluidity o f pea thylakoid membranes on PSII activity and heterogeneity. The trea tment of thylakoid membranes with cholesterol, leading to a decrease o f membrane fluidity, resulted in a decrease of the rate of PSII-mediat ed electron transport by 30% and more pronounced inhibition of PSI pho tochemical activity. These changes are accompanied by a decrease of PS II alpha centres and a decrease of the ratio F-v/F-m, obtained from th e chlorophyll fluorescence induction curves. The fluidization of the t hylakoid membranes achieved by incubation of thylakoid membranes with local anaesthetic benzyl alcohol influenced chlorophyll a fluorescence induction parameters to a smaller extent, The rates of PSI and PSII m ediated electron transport are inhibited by 20% after benzyl alcohol t reatment. The level of Q(B) nonreducing centres seems not to be altere d by either treatment. (C) 1998 Elsevier Science S.A. All rights reser ved.