Measurement of Photosynthesis in vivo with a Leaf Disc Electrode: Correlations between\nLight Dependence of Steady-State Photosynthetic O22s Evolution and Chlorophyll a\nFluorescence Transients

  • Walker D
  • Osmond C
  • 9


    Mendeley users who have this article in their library.
  • N/A


    Citations of this article.


The application of a leaf disc electrode to the measurement of the quantum yield of photosynthetic oxygen evolution (in saturating carbon dioxide concentrations) is described. The technique was also used to characterize the light-saturation curves for photosynthesis in leaves of spinach plants grown in relatively low ('shade') and high ('sun') light intensities. It was found that the flux of a blue excitation light required to elicit oscillations in chlorophyll a fluorescence corresponded, approximately, to the flux of (white) light required to saturate photosynthetic oxygen evolution. The requirement was higher for leaves of sun-grown plants (approximately 800 ,umol m-2 s-) than for shade-grown plants (approximately 200 lMmoml -2 s-l). Brief pretreatment of leaf discs from sun-grown plants with D-mannose did not change the quantum yield, but lowered the light saturated rate and the photon flux density required to saturate photosynthesis. Oscillations in fluorescence could then be observed at lower fluxes of blue excitation light, similar to those required by leaves from shade-grown plants. Photoinhibition of shade-grown plants (exposed to full sunlight for 5 h) reduced quantum yield and increased the light flux required for saturation of photosynthesis. Oscillations in fluorescence, normally observed at low fluxes of blue light in these leaves, could not be detected after photoinhibition. These correlations are interpreted and applications of the techniques described are discussed.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document


  • D A Walker

  • C B Osmond

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free