Photosystem II fluorescence: Slow changes – Scaling from the past

• Published in: Journal of photochemistry and photobiology. B, Biology Biology, 2011-07, Vol.104 (1), p.258-270
• Main Authors: Papageorgiou, George C., Govindjee
• Format: Article
• Language: English
• Subjects: carotenoids; Chlorophyll; Chlorophyll - chemistry; electrochemistry; Electron Transport; energy; fluorescence; Fluorescence induction; fluorometry; Kinetics; Magnesium - chemistry; Non-photochemical quenching; photobiology; Photochemical quenching; photochemistry; photosynthesis; photosystem II; Photosystem II Protein Complex - chemistry; Photosystem II Protein Complex - metabolism; photosystems; plant pigments; Quantum Theory; Regulation of excitation energy distribution; researchers; State transitions; thylakoids
• ISSN: 1011-1344; 1873-2682
• DOI: 10.1016/j.jphotobiol.2011.03.008

► Evolution of concepts for chlorophyll a fluorescence since photoelectric methods. ► History of the discovery of ‘state changes’ in photosynthesis. ► Direct/indirect relation of chlorophyll a fluorescence to electron transport. ► Chlorophyll a fluorescence monitors energy distribution to the two photosystems. ► Quenching/non-quenching processes as modifiers of chlorophyll a fluorescence in vivo. With the advent of photoelectric devices (photocells, photomultipliers) in the 1930s, fluorometry of chlorophyll (Chl) a in vivo emerged as a major method in the science of photosynthesis. Early researchers employed fluorometry primarily for two tasks: to elucidate the role in photosynthesis, if any, of other plant pigments, such as Chl b, Chl c, carotenoids and phycobilins; and to use it as a convenient inverse measure of photosynthetic activity. In pursuing the latter task, it became apparent that Chl a fluorescence emission is influenced (i) by redox active Chl a molecules in the reaction center of photosystem (PS) II ( photochemical quenching); (ii) by an electrochemical imbalance across the thylakoid membrane ( high energy quenching); and (iii) by the size of the peripheral antennae of weakly fluorescent PSI and strongly fluorescent PSII in response to changes in the ambient light ( state transitions). In this perspective we trace the historical evolution of our awareness of these concepts, particularly of the so-called ‘State Transitions’.