CHLOROPHYLL A FLUORESCENCE AS A QUANTITATIVE PROBE OF PHOTOSYNTHESIS: EFFECTS OF CO2 CONCENTRATION DURING GAS TRANSIENTS ON CHLOROPHYLL FLUORESCENCE IN SPINACH LEAVES

Abstract

The relationship between changes in chlorophyll a fluorescence and changes in CO2 concentration in spinach leaves is analyzed. The height of the fluorescence excursion, when plotted against the CO2 concentration during the transient, results in a hyperbola. When these data are replotted on an inverse‐reciprocal plot, an apparent Km (CO2) for the fluorescence transient can be obtained which closely approximates the Km (CO2) for carbon assimilation under similar conditions. Transitions in CO2 concentration at 2 % O2 result in deviation from this hyperbolic relationship, reducing the apparent Km (CO2) for this process. The relationship between carbon assimilation and chlorophyll fluorescence is discussed with reference to the two components of fluorescence quenching. This technique raises the possibility that chlorophyll fluorescence could be used as a quantitative as well as a qualitative tool in plant screening. Copyright © 1986, Wiley Blackwell. All rights reserved