Microscopic image instrumentation for chlorophyll a fluorescence from in situ Closterium navicula

Abstract

We have developed a new image instrumentation system of chlorophyll a fluorescence with an optical microscope, capable of in situ analysis at the cellular level. With this system we analyzed the effects of DCMU on photosynthetic activity of green alga Closterium moniliferium. The fluorescence parameters qP, qN and NPQ, and Yield, which represent photochemical quenching, non-photochemical quenching, and photosystem II photochemical efficiency, were calculated from images taken under actinic and saturating illumination. Chlorophyll fluorescence (F and F¿m) intensity of alga whose photosystem inhibited by DCMU was higher than healthy alga. The qN and NPQ was reduced greatly throughout injured alga. These results indicated the inhibition by DCMU eliminated non-photochemical quenching. In contrast, qP and Yield were not very different from healthy alga. These results showed that photochemical quenching occurred ordinarily, but Yield could not be applied as an indicator of CO2 fixation rate in such a case. It is necessary to choose the experimental condition to determine the validity of Yield.