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ABSENCE OF OXYGEN‐EVOLVING CAPACITY IN DARK‐GROWN CHLORELLA : THE PHOTO ACTIVATION OF OXYGEN‐EVOLVING CENTERS*
Author(s) -
CHENIAE G. M.,
MARTIN I. F.
Publication year - 1973
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1973.tb06378.x
Subject(s) - oxygen , photosynthesis , chlorella , oxygen evolution , quantum yield , darkness , photochemistry , pigment , photosystem , yield (engineering) , chemistry , photosystem ii , biophysics , dcmu , singlet oxygen , flashing , algae , biology , botany , materials science , biochemistry , physics , optics , fluorescence , organic chemistry , electrode , metallurgy , electrochemistry
Abstract— Chlorella cells were cultured in darkness on glucose and examined for pigment composition, capacity to evolve oxygen, and capacity to photo‐oxidize artificial electron donors to Photosystems II and I. Evidence was obtained which indicated that such cells lack oxygen‐evolving centers and the Mn pool associated with such centers but possess fully active System II and I trapping centers. Brief illumination ( t 1/2 ˜ 2–3 min) of dark‐grown cells resulted in incorporation of Mn into the O 2 ‐evolving centers and the capacity to evolve O 2 (photo‐activation). Kinetic data from flashing or continuous light showed that the photoactivation is a multi‐quantum process involving several rate limitations and a photosensitive state of limited stability. Measurements of oxygen‐yield oscillations indicated that throughout the photoactivation process each newly formed oxygen‐yielding center was independent of its neighbors. It is concluded that photoactivation of the Mn‐containing oxygen‐yielding catalyst is a fundamental process in all photosynthetic oxygen‐evolving tissue.