Study on the Photosynthetic Efficiency of the Dracontomelon Duperreanum Leaves by Using Photo-acoustic Tomography Spectroscopy

Abstract

By using a new kind of single-beam normalized photo-acoustic tomography spectroscopy (PAS-CT) technology with non-damage detection, the photo-acoustic tomography spectrum, optical absorption properties and photosynthetic pigment content of the green and yellow leaves of Dracontomelon duperreanum were studied. The photo-acoustic tomography spectrograms, obtained from different chopping frequency and sample translocation, were perfectly conform to each layer of cell’s optical absorption properties in Dracontomelon duperreanum leaves. The results showed that: the more photosynthetic pigment content the leaves of Dracontomelon duperreanum contain, the bigger optical absorption coefficient and the higher photosynthetic efficiency they have. In the research, we could find that the photosynthetic pigment content of the green leaves of Dracontomelon duperreanum is higher than that of the yellow ones. As a result, the optical absorption coefficient and the photosynthetic efficiency of the green ones were higher than the yellow ones. The photo-acoustic tomography spectroscopy could be a kind of non-damage detection to confirm the growth of trees. According to the results of our research, the photosynthetic efficiency of Dracontomelon duperreanum could be improved and its growth time could be effectively controlled. And it provides foundations to cultivate Dracontomelon duperreanum effectively. Furthermore, it could make benefits to the controlled environmental forestry and increase forest production to meet the need of forest for 7 billion people. The research showed high science value to the study and application of the photosynthesis of plants. Introduction Photo-acoustic tomography spectroscopy (PAS-CT) is a new kind of spectroscopic technique with non-damage detection. If we measure the spectral absorption coefficient of leaves by the traditional absorption spectrometry, obstacles would be met by the interference of scattered light. As the photo-acoustic spectroscopy measures the heat from the material after absorption of light which is irrelevant to the scattered light, its influence could be avoided. So it is suitable for the spectral detection and analysis of strong scatter and opaque substances such as leaves, particles, powders, stains and other strong scattering turbid liquid. this methods can avoid. It will be a new method to study photosynthetic efficiency of plant. And it has the advantages of high sensitivity, high universality and non-destructive measurement. As a result, it will be widely applied in material science [1-3], biomedical [4-8], agriculture and forestry and other fields. In this paper, the International Conference on Material Science and Application (ICMSA 2015) © 2015. The authors Published by Atlantis Press 687 photo-acoustic tomography spectroscopy (PAS-CT) of Dracontomelon duperreanum leaves and its chromatography optical absorption coefficient were measured. The study of the optical properties of leaves is to reveal a more effective way to detect the growth of trees in non-damaging way, and improve the leaves’ capacity of absorbing light. Experimental Principle of Photoacoustic Tomography Spectroscopy According to Rosencwaig-Gersho (R-G) theory [9,10], when the substances (samples) modulators are alternating light heating, some of the heat flow through the thermal conductivity of gas with it. As the attenuation of the heat wave is a fast wave, only the thin surface layer of material in contact with the gas get this kind of alternating heat. And by heat, this thin layer, as the alternating heating and vibration undergo, like a vibration pistons firing sound waves, generate the photo-acoustic signal. R-G is based on the theory. Suppose the sample and reference samples testing photo-acoustic signals are ) ( ) ( λ λ c s S S 、 : ) ( ) ( ) ( λ β λ λ s s CI S = (1) c c CI S β λ λ ) ( ) ( = (2) Samples which are used and the reference sample absorption spectrum coefficients is c s β λ β ), ( . C is the ratio of the experimental conditions of the coefficients. ) (λ I is the light intensity. As the reference sample (carbon black) of the absorption coefficients c β is not related to the wavelength, which c β is a constant [11], and so the sample of carbon black by the photo-acoustic signal intensity only with the light source, and the wavelength. Photo-acoustic signal of carbon black ) (λ c S is the power spectrum of xenon lamp. In order to eliminate the power spectrum of the light source, we use the normalized photo-acoustic spectroscopy, which uses photo-acoustic signal of the sample divided by the photo-acoustic signal of carbon black: