Application of modulated photoacoustic spectroscopy to measurement of photochemical quenching of variable thermal emission in thylakoid membranes during heat or light stress

Abstract

The application of photoacoustic spectroscopy to the study of photosynthesis in thylakoid membranes is well documented in the literature. We use various parameters to compare the quenching of variable fluorescence with the energy storage measured by photoacoustic spectroscopy to gain more information about their interrelationship. The use of thylakoid membranes and photosystem II (PSII) enriched submembrane fractions pretreated at various temperatures or exposed to photoinhibitory illumination indicates that there is a strong correlation between the photochemical quenching of variable fluorescence and that of variable thermal dissipation. However, some differences also exist that are likely due to the involvement of cyclic electron transport in both photosystem I and PSII during the formation of energy storage and to the fact that energy storage is more influenced by the reduction of the plastoquinone pool, whereas variable fluorescence depends solely on the redox state of the primary photosystem II acceptor QA .