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. 1985 May;78(1):71–75. doi: 10.1104/pp.78.1.71

O2-Insensitive Photosynthesis in C3 Plants 1

Its Occurrence and a Possible Explanation

Thomas D Sharkey 1
PMCID: PMC1064678  PMID: 16664211

Abstract

Leaves of C3 plants which exhibit a normal O2 inhibition of CO2 fixation at less than saturating light intensity were found to exhibit O2-insensitive photosynthesis at high light. This behavior was observed in Phaseolus vulgaris L., Xanthium strumarium L., and Scrophularia desertorum (Shaw.) Munz. O2-insensitive photosynthesis has been reported in nine other C3 species and usually occurred when the intercellular CO2 pressure was about double the normal pressure. A lack of O2 inhibition of photosynthesis was always accompanied by a failure of increased CO2 pressure to stimulate photosynthesis to the expected degree. O2-insensitive photosynthesis also occurred after plants had been water stressed. Under such conditions, however, photosynthesis became O2 and CO2 insensitive at physiological CO2 pressures. Postillumination CO2 exchange kinetics showed that O2 and CO2 insensitivity was not the result of elimination of photorespiration.

It is proposed that O2 and CO2 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. Under these conditions, the energy diverted to photorespiration does not adversely affect the potential for CO2 assimilation.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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