A laser diode fluorometer for field measurements of the F685/F730 chlorophyll fluorescence ratio

This article presents a new fluorometer developed for the simultaneous measurement of the two peaks of chlorophyll fluorescence (685 and 730 nm). The instrument is compact, battery operated, and easy to carry for field use. A diode laser at 635 nm excites the fluorescence through a single optical fiber. The same fiber also collects fluorescence, which is detected by two photodiodes with wavelengths selected by interference and long pass filters. A microprocessor controls the instrument and stores data in static random access memory, for a later backup on an external PC. The pre-processing software allows real time display of the F685/F730 fluorescence ratio and of the fluorescence induction parameters. Some typical examples of applications on plant physiology and stress detection are discussed, together with proposed experimental procedures and their interpretation.