Characterisation of the effects of Antimycin A upon high energy state quenching of chlorophyll fluorescence (qE) in spinach and pea chloroplasts.

High energy state quenching of chlorophyll fluorescence (qE) is inhibited by low concentrations of the inhibitor antimycin A in intact and osmotically shocked chloroplasts isolated from spinach and pea plants. This inhibition is independent of any effect upon ΔpH (as measured by 9-aminoacridine fluorescence quenching). A dual control of qE formation, by ΔpH and the redox state of an unidentified chloroplast component, is implied. Results are discussed in terms of a role for qE in the dissipation of excess excitation energy within photosystem II.