LIGHT-INDUCED QUENCHING OF PHOTOSYSTEM II FLUORESCENCE AT 77 K |
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Authors: | David J.,Kyle ,Charles J.,Arntzen ,Fabrice,Franck&dagger Y. Inoue |
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Affiliation: | Laboratory of Plant Physiology, Institute of Physical and Chemical Research, Rikagaku Kenkyushu, Wako-Shi. Saitama 351, Japan;*MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA;†Laboratory of Photobiology, The University, Sart Tilman, B4000, Liege, Belgium |
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Abstract: | Abstract— Light-induced quenching of the low temperature fluorescence emission from photosystem II (PS II) at 695 nm ( F 695) has been observed in chloroplasts and whole leaves of spinach. Photosystem I (PS I) fluorescence emission at 735 nm ( F 735) is quenched to a lesser degree but this quenching is thought to originate from PS II and is manifest in a reduced amount of excitation energy available for spillover to PS I. Differential quenching of these two fluorescence emissions leads to an increase in the F 735/ F 685 ratio on exposure to light at 77 K. Rewarming the sample from -196°C discharges the thermoluminescence Z-band and much of the original unquenched fluorescence is recovered. The relationship between the thermoluminescence Z-band and the quenching of the low temperature fluorescence emission ( F 695) is discussed with respect to the formation of reduced pheophytin in the PS II reaction center at 77 K. |
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