Although the newly developed beam deflection/fluorescence detection system for real-time insitu simultaneous monitoring of dissolved oxygen (DO) and materials movements at a vicinity of aquatic plants was not only much more sensitive but also 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 photosynthesis process of aquatic plants yet. Here, its improvements are reported to be able to apply 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 660nm and 450nm. Also, an interference filter of 589±25nm 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 increase in 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 materials moments-induced beam deflection at vicinity of the plants in both the respiration and photosynthesis processes could be real-time in-situ monitored with high sensitivity.

Recently we developed a novel optical detection system that allowed real-time in-situ simultaneous monitoring of dissolved oxygen and materials movements at a vicinity of micrometers from an aquatic plant by combining deflection of a probe beam and fluorescence quenching. In the detection system, dissolved oxygen (DO)-quenched fluorescence was monitored together with beam deflection signals at the vicinity of the plant, then DO concentration was calculated from the fluorescence intensity. Here, three calculation methods for obtaining DO concentrations from the fluorescence intensity were examined. Results showed that exponential equations method, where fluorescent quenching coefficient and measured fluorescence intensity either with or without DO were approximated with exponential equations of temperature, gave the closest results to the measured ones by a DO sensor. The method was further applied to monitoring of oxygen and materials movement across the aquatic plants surface.