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Plant Physiol. Dec 1984; 76(4): 968–971.
PMCID: PMC1064417

Photosynthesis and Ribulose 1,5-Bisphosphate Concentrations in Intact Leaves of Xanthium strumarium L. 1


The interacting effects of the rate of ribulose 1,5-bisphosphate (RuBP) regeneration and the rate of RuBP utilization as influenced by the amount and activation of RuBP carboxylase on photosynthesis and RuBP concentrations were resolved in experiments which examined the kinetics of the response of photosynthesis and RuBP concentrations after step changes from a rate-saturating to a rate-limiting light intensity in Xanthium strumarium. Because RuBP carboxylase requires several minutes to deactivate in vivo, it was possible to observe the effect of reducing the rate of RuBP regeneration on the RuBP concentration at constant enzyme activation state by sampling very soon after reducing the light intensity. Samples taken over longer time periods showed the effect of changes in enzyme activation at constant RuBP regeneration rate on RuBP concentration and photosynthetic rate. Within 15 s of lowering the light intensity from 1500 to 600 microEinsteins per square meter per second the RuBP concentration in the leaves dropped below the enzyme active site concentration, indicating that RuBP regeneration rate was limiting for photosynthesis. After longer intervals of time, the RuBP concentration in the leaf increased as the RuBP carboxylase assumed a new steady state activation level. No change in the rate of photosynthesis was observed during the interval that RuBP concentration increased. It is concluded that the rate of photosynthesis at the lower light intensity was limited by the rate of RuBP regeneration and that parallel changes in the activation of RuBP carboxylase occurred such that concentrations of RuBP at steady state were not altered by changes in light intensity.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Farquhar GD. Models describing the kinetics of ribulose biphosphate carboxylase-oxygenase. Arch Biochem Biophys. 1979 Apr 1;193(2):456–468. [PubMed]
  • Miziorko HM, Lorimer GH. Ribulose-1,5-bisphosphate carboxylase-oxygenase. Annu Rev Biochem. 1983;52:507–535. [PubMed]
  • Perchorowicz JT, Raynes DA, Jensen RG. Light limitation of photosynthesis and activation of ribulose bisphosphate carboxylase in wheat seedlings. Proc Natl Acad Sci U S A. 1981 May;78(5):2985–2989. [PMC free article] [PubMed]
  • Perchorowicz JT, Jensen RG. Photosynthesis and Activation of Ribulose Bisphosphate Carboxylase in Wheat Seedlings : Regulation by CO(2) and O(2). Plant Physiol. 1983 Apr;71(4):955–960. [PMC free article] [PubMed]
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Articles from Plant Physiology are provided here courtesy of American Society of Plant Biologists


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