Relationship of fluorescence and thermal emission from isolated thylakoids under light stress conditions.

Simultaneous measurements of fluorescence and thermal emission have been made by a combined fluorescence and photoacoustic techniques on isolated thylakoids pretreated by a prolonged illumination of saturating light. The traces of the signals are used to calculate four characteristic parameters, energy storage, half-saturation intensity, number of photons to close reaction center, and a constant for quasi-equlibria between (re)oxidized and reduced quinone acceptors. These parameters are used to study the response of photosynthetic apparatus functioning under photoinhibition stress. The defense mechanism seems to possess an efficient cooperativity of reaction centers under stress conditions.