Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Use of a Light-Induced Respiratory Transient to Measure the Optical Cross Section of Photosystem I in Chlorella

Nancy L. Greenbaum, Arthur C. Ley and David C. Mauzerall
Plant Physiology
Vol. 84, No. 3 (Jul., 1987), pp. 879-882
Stable URL: http://www.jstor.org/stable/4270733
Page Count: 4
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Use of a Light-Induced Respiratory Transient to Measure the Optical Cross Section of Photosystem I in Chlorella
Preview not available

Abstract

A method has been developed whereby the magnitude of a transient in O2 uptake attributable to photosystem (PS) I activity, following single-turnover laser flashes of varying energy, can be used to measure the optical cross section of PSI. As measurements are made under the identical physiological conditions for which the cross section of PSII has previously been determined (AC Ley, DC Mauzerall 1982 Biochim Biophys Acta 680:96-105), it is now possible to simultaneously measure the cross section of both photosystems in intact, photosynthetically competent cells, without the use of inhibitors or artificial mediators of electron transport. Plots of light-saturation behavior of the respiratory oscillation following pulses at 596 nanometers indicate a mean optical cross section similar to that of PSII at this wavelength, but suggest significant heterogeneity in the cross section of PSI. If this method measures only PSI activity, this result implies that there exist units with different numbers of identical chromophores, or units having populations of chromophores with different absorption spectra.

Page Thumbnails

  • Thumbnail: Page 
879
    879
  • Thumbnail: Page 
880
    880
  • Thumbnail: Page 
881
    881
  • Thumbnail: Page 
882
    882