The transient fluorescence is a phenomenon that occurs when a photosynthetic material is suddenly exposed to a light source after a dark adaptation time. Under these conditions, photosynthetic materials emit fluorescence passing from an initial value to a maximum value through a series of intermediate steps. This fluorescence curve (called "Kautsky curve") can be used to individuate various stress conditions over the biological material as, for example, those due to the presence of contaminants such as herbicides. This article describes the design, development and validation of a multi-cell instrument capable of simultaneously measuring and characterizing the Kautsky curve of different photosynthetic organisms (algae, in particular). Instrument design, validation, as well as results obtained using standard and real samples are shown. The target application here reported is the algae-based in situ measurement of water samples for herbicides detection, but the concept of "modular instrument" permits to adapt it to other type of photosynthetic mediators or conventional fluorescence markers for many different future applications.
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