Energetic Factors Affecting Carbon Dioxide Fixation in Isolated Chloroplasts 1
AUTOR(ES)
Slovacek, Rudolf E.
RESUMO
Light- and HCO3−-saturated (10 millimolar) rates of O2 evolution (120 to 220 micromoles O2 per milligram chlorophyll per hour), obtained with intact spinach chloroplasts, are decreased up to 3-fold by changes in assay conditions such as omission of catalase from the medium, the use of high (≥1 millimolar) inorganic phosphate, inclusion of NO2− as an electron acceptor, or bright illumination at low partial pressures of O2. These inhibitions may be reversed by addition of uncoupling levels of NH4Cl or of antimycin concentrations that partially block cyclic electron transfer between cytochrome b6 and cytochrome f. Measurements of the pH gradient across the thylakoid membrane with the fluorescent probe, 9-aminoacridine, indicate that changes in ΔpH are sufficient to account for both the inhibited and restored rates of electron transport. It follows that the rate of HCO3−-saturated photosynthesis may be restricted by a proton gradient back pressure under these conditions.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=440369Documentos Relacionados
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