Chlorophyll A Laser Photoluminescence Of The Photoelectric Detection System And Its Application

Chlorophyll a is an activator of the photosynthesis of plants. Chlorophyll a content in the water that determined the amount of phytoplankton is one of the most important indices to monitor the water quality of the ocean, it also can estimate the primary productivity in the ocean with the chlorophyll a content. Consequently, it can forecast the appearance of the red tide. Moreover, Chlorophyll a content in plants, which can represent the photosynthetic activity of green plants, is a significant parameter to monitor the growing state of plants. Therefore, it is much important to research on the measurement of the chlorophyll a content. For a long time, the usual methods to measure the concentration of chlorophyll a are the spectrophotometry and fluorometry. The former cannot be applied on real-time measurement due to the poor sensitivity, the long measurement cycle and the disturbance of other pigment. So the researchers now often use fluorometry to measure the chlorophyll a content in the water. But for the measurement of the chlorophyll a content of plants there is almost not any new methods to be mentioned and the spectrophotometry is still be used. In this dissertation, based on the theory of laser-induced chlorophyll a fluorescence character, we first use the red laser diode with low energy consumption as excited light combining a Fiber-optic spectrometer to enhance the ability of collecting the fluorescence signal, and then introduce the chlorophyll a fluorescence intensity 685 nm and the fluorescence intensity ratio F685/F735 to evaluate the chlorophyll a relative content in the water and green leaves separately. Additionally, we conclude the regression equation between chlorophyll a content and the relative fluorescence intensity ratio F685/F735 by the least squares method, further develop a new method to measure the chlorophylly a content quantificationally. The study content and innovations in this dissertation contain:1. Theoretically, on the basis of analyzing the principle of laser-induced chlorophyll fluoscence and the technique of fluorometry, we put forward the method using two parameters, the 685 nm relative fluoscence intensity and the fluorescence intensity ratio F685/F735, to evaluate the chlorophyll a relative content in the water and green leaves separately. The experimental results indicate that it is feasible to give a fast and visualjudgement for chlorophyll content, because of its better accuracy and sensitivity, it further gives a theoretical foundation of on-spot monitoring the chlorophyll a content in the ocean or in green leaves.2. In this dissertation, we construct a set of photoelectric measurement system on chlorophyll a content based on the theory that mentioned in the paper, and also compile the software interface of fluoscence spectrums and data processing. Moreover, we analyze and optimize the system performance, and take the experiments on testing the chlorophyll a content in the water and plants. The results show that the system is applicable to test the content of chlorophlly a both in water and plants, due to its advantages of the simple structure and operation, excellent stability, etc.3. In the field of measuring chlorophyll a content of green plants, we first take a quantificationally measurement on chlorophyll a content of green plants combining the fluorometry, namely: first conclude the regression equation between chlorophyll a content (from the known sample or has been tested beforehand) and the corresponding fluorescence intensity ratio F685/F735 by the least squares method, and then use the fluorescence intensity ratio of the under test sample to substitute the equation, thus, it can figure out the actual chlorophyll a content(μg/cm~2). It is verified to be very feasible by experiments, furthermore, this method has higher sensitivity, less error, more simply and shorter testing cycle than the traditional spectrophotometry, and compared with the chlorophyll meter, it is more applicable to the situation which need to be made a quantitative calculation on measuring chlorophyll a content.