Photosynthesis in Isolated Chloroplasts of the Crassulacean Acid Metabolism Plant Sedum praealtum1
AUTOR(ES)
Spalding, Martin H.
RESUMO
Intact chloroplasts were isolated from protoplasts of the Crassulacean acid metabolism plant Sedum praealtum D.C. Typical rates of CO2 fixation or CO2-dependent O2 evolution ranged from 20 to 30 micromoles per milligram chlorophyll per hour and could be stimulated 30 to 50% by several Calvin cycle intermediates. The pH optimum for CO2 fixation was 7.0 to 7.6 with considerable activity as low as pH 6.4. Low concentrations of orthophosphate (Pi) (optimum 0.4 millimolar) stimulated photosynthesis while high concentrations (5 millimolar) caused some inhibition. Both CO2 fixation and CO2-dependent O2 evolution exhibited a relatively long lag phase (4 to 6 minutes) which remained constant between 0.4 to 5 millimolar Pi. The lag phase could be decreased by addition of dihydroxyacetone-phosphate or ribose 5-phosphate. Further results are presented which suggest these chloroplasts have a functional phosphate translocator.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=440477Documentos Relacionados
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