Abstract
Fluorescence quantum yield measurements, like pulse amplitude modulation fluorometry, has been extensively used to study physiological status of thylakoid membranes. However, there may be still some improvements for characterizing thylakoid membranes under high magnification microscope. In our efforts to obtain morphological and spectral information at the same time on single cellular basis, we have added a new functionality of absorption spectral detection to our fluorescence spectral microscope. An automatic filter wheel was installed in the illumination pathway by a halogen lamp, by which transmission at 11 colors were efficiently obtained to determine absorption spectra mainly associated with absolute concentration of chlorophylls. We have applied this methodology to cyanobactrium Anabaena variabilis and green alga Chlorella kessleri, both of which are known to grow under dark conditions if some organic nutritions are supplied. In comparison between cells grown photoautotrophically and heterotrophically, we have found systematic changes in the morphology and photochemical status of the thylakoid membranes.
