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. 1980 Mar;65(3):489–494. doi: 10.1104/pp.65.3.489

Photosynthetic and Photorespiratory Carbon Metabolism in Mesophyll Protoplasts and Chloroplasts Isolated from Isogenic Diploid and Tetraploid Cultivars of Ryegrass (Lolium perenne L.) 1

C K M Rathnam 1,2, Raymond Chollet 1,3
PMCID: PMC440361  PMID: 16661220

Abstract

Photosynthetic 14CO2 fixation, [14C]glycolate formation, and the decarboxylation of [1-14C]glycolate and [1-14C]glycine by leaf mesophyll protoplasts isolated from isogenic diploid and tetraploid cultivars of ryegrass (Lolium perenne L.) were examined. The per cent O2 inhibition of photosynthesis in protoplasts from the tetraploid cultivar was less than that of the diploid line at both 21 and 49% O2. Kinetic studies revealed that the Km (CO2) for photosynthesis by the diploid protoplasts was about twice that of the tetraploid line. In contrast, the Ki (O2) for protoplast photosynthesis was similar in both cultivars, as was the potential for oxidizing glycolate and glycine to CO2 via the photorespiratory carbon oxidation cycle. Although the maximal rates of glycolate accumulation by the isolated protoplasts in the presence of 21% O2 and a glycolate oxidase inhibitor were similar in the two cultivars, the percentage of total fixed 14C entering the [14C]glycolate pool and the ratio of the rate of [14C]glycolate formation to 14CO2 fixation at 21% O2 and low pCO2 were about two times greater in protoplasts and intact chloroplasts isolated from the diploid line compared to the tetraploid. These results fully support the recent observation that a doubling of ploidy in various ryegrass cultivars reduced the Km (CO2) of purified ribulose bisphosphate carboxylase-oxygenase by about one-half without affecting the Ki (O2) (Garrett 1978 Nature 274: 913-915).

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Selected References

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

  1. Chollet R. 14CO2 fixation and glycolate metabolism in the dark in isolated maize (Zea mays L.) bundle sheath strands. Arch Biochem Biophys. 1974 Aug;163(2):521–529. doi: 10.1016/0003-9861(74)90510-4. [DOI] [PubMed] [Google Scholar]
  2. Chollet R. Effect of glycidate on glycolate formation and photosynthesis in isolated spinach chloroplasts. Plant Physiol. 1976 Feb;57(2):237–240. doi: 10.1104/pp.57.2.237. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Edwards G. E., Robinson S. P., Tyler N. J., Walker D. A. Photosynthesis by isolated protoplasts, protoplast extracts, and chloroplasts of wheat: influence of orthophosphate, pyrophosphate, and adenylates. Plant Physiol. 1978 Aug;62(2):313–319. doi: 10.1104/pp.62.2.313. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Jewess P. J., Kerr M. W., Whitaker D. P. Inhibition of glycollate oxidase from pea leaves. FEBS Lett. 1975 May 15;53(3):292–296. doi: 10.1016/0014-5793(75)80039-1. [DOI] [PubMed] [Google Scholar]
  5. Laing W. A. Regulation of Soybean Net Photosynthetic CO(2) Fixation by the Interaction of CO(2), O(2), and Ribulose 1,5-Diphosphate Carboxylase. Plant Physiol. 1974 Nov;54(5):678–685. doi: 10.1104/pp.54.5.678. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Randall D. D., Nelson C. J., Asay K. H. Ribulose bisphosphate carboxylase: altered genetic expression in tall fescue. Plant Physiol. 1977 Jan;59(1):38–41. doi: 10.1104/pp.59.1.38. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Rathnam C. K., Chollet R. Phosphoenolpyruvate carboxylase reduces photorespiration in Panicum milioides, a C3-C4 intermediate species. Arch Biochem Biophys. 1979 Apr 1;193(2):346–354. doi: 10.1016/0003-9861(79)90039-0. [DOI] [PubMed] [Google Scholar]
  8. Rathnam C. K., Chollet R. Photosynthetic carbon metabolism in Panicum milioides, a C3-C4 intermediate species: evidence for a limited C4 dicarboxylic acid pathway of photosynthesis. Biochim Biophys Acta. 1979 Dec 6;548(3):500–519. doi: 10.1016/0005-2728(79)90061-6. [DOI] [PubMed] [Google Scholar]
  9. Servaites J. C. Chemical inhibition of the glycolate pathway in soybean leaf cells. Plant Physiol. 1977 Oct;60(4):461–466. doi: 10.1104/pp.60.4.461. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Slabas A. R., Walker D. A. Inhibition of spinach phosphoribulokinase by DL-glyceraldehyde. Biochem J. 1976 Mar 1;153(3):613–619. doi: 10.1042/bj1530613. [DOI] [PMC free article] [PubMed] [Google Scholar]

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