Recording microphotometer for determination of light induced chromatophore movements in brown algae

Abstract

A recording microphotometer for measuring the reaction amplitude and the kinetics of light induced chromatophore movements is described. It consists essentially of a Zeiss universal microscope which is equipped with a photomultiplier to detect the transmission changes in the test object caused by the light induced chromatophore displacement. Long term experiments are enabled by setting the light program with the aid of an automated filter change. As object the brown alga Dictyota dichotoma was used. To study the object under nearly natural conditions it is incorporated into a flow-through cuvette coupled with a recycling system for nutrient medium supply and gas exchange. Long term experiments demonstrated that the test object still gave good reactions after about 1 month experimental treatment. In all experiments notable differences in the kinetics of high and low intensity movement have been observed. Intensity/reaction-amplitude experiments showed that the extreme high intensity arrangement is achieved at irradiation levels between 12,000 and 23,000 lux, whereas the extreme low intensity arrangement was found between 500 and 2000 lux, both depending on the sensitivity of the individual object investigated.