Delayed fluorescence (DF) is a characteristic feature of light-excited plant cells caused by the back-reaction of electrons through the electron transport chain. Targeting the response of light-adapted green algae to diurnal light changes, the present study presents novel results of DF measurements in the absence of an artificial excitation light source. Based on a linear relationship between the DF counts and light intensities from 0.15 to 0.65 W m–2 during daybreak, we estimated an initial algal response to light intensities of 0.01 W m–2. Dissolved oxygen concentrations began to increase at 1.0 W m–2. A noon depression similar to that reported for prompt fluorescence occurred above 100 W m–2. Our results from multiple day–night cycles emphasize that the DF response is a function of the chlorophyll concentration and of a rapid light adaptation. The DF counts alone cannot provide a reliable unambiguous measure of photosynthetic activity.
Bibliographical noteFunding Information:
The present study was supported research grant #: WT 1003/2264 from the German Federal Ministry of Education and Research (BMBF) and Israel Ministry of Science and Technology (MOST).
Abbreviations: Chl – chlorophyll; DF – delayed fluorescence; DFI – delayed fluorescence integral; ETC – electron transport chain; n-DFI – normalized delayed fluorescence integral; PP – primary production. Acknowledgements: The present study was supported research grant #: WT 1003/2264 from the German Federal Ministry of Education and Research (BMBF) and Israel Ministry of Science and Technology (MOST).
© The authors.
- Additional Chlorella vulgaris
- Chlorophyll fluorescence
- Diurnal light cycle
ASJC Scopus subject areas
- Plant Science