Chlorophyll fluorescence analysis in Euglena gracilis: a survey on the use of a portable PAM fluorometer for photosynthesis studies in flagellate algae.

A chlorophyll fluorescence analysis has been performed in Euglena gracilis using a portable PAM fluorometer. For analyses, the cells were collected on glass-fiber filters. The method employed allowed confirmation of the special properties characterizing the chlorophyll fluorescence emission in the organism. Most interesting aspects were: 1. the induction of non-photochemical quenching in darkness; 2. the good ability to maintain open the PSII over a wide range of irradiance; 3. the dissection of three components originating the non-photochemical quenching (energy, state transition, and photoinhibitory quenches). Under high irradiance, photoinhibition of PSII units played a major role in determining the non-photochemical quenching. For this reason, during relaxation only a partial recovery of PSII quantum yield was observed. Since the results were consistent with the data available in literature, with only some discrepancies due to different experimental procedures, the use of the portable PAM fluorometer can be proposed as a valid alternative to conventional PAM fluorometers for the study of fluorescence properties in flagellate algae.