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Title: O/sub 2/-insensitive photosynthesis in C/sub 3/ plants: its occurrence and a possible explanation. [Phaseolus vulgaris; Xanthium strumarium L. ; Scrophularia desertorum (Shaw. ) Munz]

Leaves of C/sub 3/ plants which exhibit a normal O/sub 2/ inhibition of CO/sub 2/ fixation at less than saturating light intensity were found to exhibit O/sub 2/-insensitive photosynthesis at high light. This behavior was observed in Phaseolus vulgaris L., Xanthium strumarium L., and Scrophularia desertorum (Shaw.) Munz. O/sub 2/-insensitive photosynthesis has been reported in nine other C/sub 3/ species and usually occurred when the intercellular CO/sub 2/ pressure was about double the normal pressure. A lack of O/sub 2/ inhibition of photosynthesis was always accompanied by a failure of increased CO/sub 2/ pressure to stimulate photosynthesis to the expected degree. O/sub 2/-insensitive photosynthesis also occurred after plants had been water stressed. Under such conditions, however, photosynthesis became O/sub 2/ and CO/sub 2/ insensitive at physiological CO/sub 2/ pressures. Postillumination CO/sub 2/ exchange kinetics showed that O/sub 2/ and CO/sub 2/ insensitivity was not the result of elimination of photorespiration. It is proposed that O/sub 2/ and CO/sub 2/ insensitivity occurs when the concentration of phosphate in the chloroplast stroma cannot be both high enough to allow photophosphorylation and low enough to allow starch and sucrose synthesis at the rates required by the rest of the photosynthetic component processes. Undermore » these conditions, the energy diverted to photorespiration does not adversely affect the potential for CO/sub 2/ assimilation.« less
Authors:
Publication Date:
OSTI Identifier:
5022641
DOE Contract Number:
FG08-84ER13234
Resource Type:
Journal Article
Resource Relation:
Journal Name: Plant Physiol.; (United States); Journal Volume: 78:1
Research Org:
Desert Research Institute, Reno, Nevada
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; OXYGEN; BIOLOGICAL EFFECTS; PHOTOSYNTHESIS; INHIBITION; VISIBLE RADIATION; RESPONSE MODIFYING FACTORS; CARBON DIOXIDE FIXATION; CHLOROPLASTS; EXPERIMENTAL DATA; GAS FLOW; LEAVES; PHOSPHATES; RESPIRATION; WATER; CELL CONSTITUENTS; CHEMICAL REACTIONS; DATA; ELECTROMAGNETIC RADIATION; ELEMENTS; FLUID FLOW; HYDROGEN COMPOUNDS; INFORMATION; NONMETALS; NUMERICAL DATA; OXYGEN COMPOUNDS; PHOSPHORUS COMPOUNDS; PHOTOCHEMICAL REACTIONS; RADIATIONS; SYNTHESIS 550501* -- Metabolism-- Tracer Techniques