Improvements on the Fluorescence Quenching/Deflection Method for Real-time in situ Simultaneous Monitoring of Dissolved Oxygen and Material Movement induced Beam Deflection in the Vicinity of an Aquatic Plant

Although the newly developed beam deflection/fluorescence detection system for real-time in situ simultaneous monitoring of dissolved oxygen (DO) and material movements in the vicinity of aquatic plants was not only much more sensitive but also could be carried out much more closely to real time than conventional analytical methods that monitor the concentration changes at a bulk solution, it could not be applied to the photosynthesis process of aquatic plants. Here, improvements are reported to enable application of the system to the photosynthesis process. A white-light LED, which was used as a light source for photosynthesis in our previous paper, was replaced by a red-blue LED with wavelength of about 660 and 450 nm. Also, an interference filter of 589 +/- 25 nm was placed in front of a photomultiplier tube (PMT). Furthermore, the LED and its electric power supply were placed outside of the dark room for preventing great temperature increases in the photosynthetic experiments. Experimental results showed the DO-quenched fluorescence could be sensitively monitored in both the respiration and photosynthesis processes, while only in the respiration process before the improvements. It is successfully demonstrated that the DO change and material movement-induced beam deflection in the vicinity of the plants in both the respiration and photosynthesis processes could be real-time in situ monitored with high sensitivity.