This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Huber, S. C. Search for Related Content PubMed PubMed Citation Articles by Huber, S. C. Agricola Articles by Huber, S. C.

Articles

Effect of Photosynthetic Intermediates on the Magnesium Inhibition of Oxygen Evolution by Barley Chloroplasts ¹

^a United States Department of Agriculture, Science and Education Administration, Agriculture Research, Departments of Crop Science and Botany, North Carolina State University, Raleigh, North Carolina 27650

Millimolar concentrations of Mg²⁺ inhibited CO₂-dependent O₂ evolution by barley (Hordeum vulgare L.) chloroplasts and also prevented the activation of NADP-glyceraldehyde-3-phosphate dehydrogenase, ribulose-5-phosphate kinase, and fructose-1,6-diphosphatase by light in intact chloroplasts. When added in the dark, 3-phosphoglycerate prevented the inhibition of O₂ evolution by Mg²⁺ and reduced the Mg²⁺ inhibition of enzyme activation by light. Fructose 1,6-diphosphate and ribulose 5-phosphate also prevented the inhibition of O₂ evolution by Mg²⁺ whereas glucose 1-phosphate, glucose 6-phosphate, ribulose 1,5-diphosphate, and citrate had no effect. Phosphoenolpyruvate gave an intermediate response. Metabolites that prevented the Mg²⁺ inhibition of O₂ evolution shortened the lag phase of CO₂-dependent O₂ evolution in the absence of M²⁺. Loading chloroplasts in the dark with 3-phosphoglycerate reduced both the lag phase of O₂ evolution and the inhibition of O₂ evolution by Mg²⁺. The results suggested that Mg²⁺ inhibition was lessened either by external metabolites that compete with inorganic phosphate for transport into the chloroplast or by a high concentration of internal metabolites.