ZEAXANTHIN DEPENDENT AND ZEAXANTHIN INDEPENDENT CHANGES IN NONPHOTOCHEMICAL ENERGY-DISSIPATION

The influence of zeaxanthin on high-energy-state quenching (q(E)) of r oom temperature chlorophyll fluorescence and on the quantum yield of o xygen evolution(Phi(O2)) has been studied with isolated spinach thylak oids. A set of three different pretreatments was tested which all led to thylakoids with high contents of zeaxanthin. Depending on the prese nce of light the pretreatments differed strongly with respect to their effect on nonphotochemical fluorescence quenching. Independently from the extent of changes in nonphotochemical energy dissipation in the m embrane energized state as reflected by nonphotochemical quenching the light pretreatments caused also changes in nonphotochemical energy di ssipation in the nonenergized state as measured by the quantum yield o f oxygen evolution (Phi(O2)) in uncoupled thylakoids. Zeaxanthin was n ot involved in the decrease of (Phi(O2)).