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CONTROL OF PHOTOSYNTHETIC REDUCTANT: THE ROLE OF LIGHT AND TEMPERATURE ON SUSTAINED HYDROGEN PHOTOEVOLUTION BY Chlamydomonas sp. IN AN ANOXIC, CARBON DIOXIDE‐CONTAINING ATMOSPHERE *
Author(s) -
Graves Duane A.,
Tevault Carol V.,
Greenbaum Elias
Publication year - 1989
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.1751-1097.1989.tb05566.x
Subject(s) - photosynthesis , carbon dioxide , hydrogen , chlamydomonas reinhardtii , anoxic waters , electron transport chain , chemistry , atmosphere (unit) , light intensity , photochemistry , botany , biology , environmental chemistry , biochemistry , organic chemistry , physics , mutant , optics , gene , thermodynamics
–Sustained hydrogen photoevolution from Chlamy domonas reinhardtii and C. Moewusii was measured under an anoxic, CO 2 ‐containing atmosphere. It has been discovered that light intensity and temperature influence the partitioning of reductant between the hydrogen photoevolution pathway and the Calvin cycle. Under low incident light intensity (1‐3 W m ‐2 ) or low temperature (approx. 0°C), the flow of photosynthetic reductant to the Calvin cycle was reduced, and reductant was partitioned to the hydrogen pathway as evidenced by sustained H 2 photoevolution. Under saturating light (25 W m ‐2 ) and moderate temperature (20±5°C), the Calvin cycle became the absolute sink for reductant with the exception of a burst of H 2 occurring at light on. This burst of H 2 corresponded to the expression of about 450 electrons for each photosynthetic electron transport chain. These results suggest that the hydrogen pathway and the Calvin cycle compete for reductant under anoxic conditions and that partioning between the two pathways can, to a certain extent, be controlled by the appropriate choice of experimental conditions.