| Delayed Fluorescence (DF), which is also referred to as "delayed luminescence (DL)" and "delayed light emission (DLE)", is a long-lived low-level photon emission by plant after being illuminated with light and put into darkness and only occurs in living cells. DF generation involves the process of energy absorption, transfer, storage, and reemission. DF is intrinsically related to the photosynthesis process, and it is a good method of researching the effect of various chemical and physical factors in vivo and in vitro on photosynthetic performance of plants. At present, DF has been wide applied in the research of biomedicine, agriculture, food industry, and environment and so on.In this thesis, the DF detection technique and its application are taken as core. The detection method of DF decay signals, the relation between DF intensity and net photosynthetic rate (Pn), and the changes of DF intensity and F730/F685 ratio of DF emission spectra under the stress (heat, salt and UV-B) have been investigated in different plant species. The following contents are the major research works of this thesis:1. Based on DF decay kinetics rule, a system of DF detection with the ability to measure the DF signal of plant leaf, easy change the excitation light source and settle environmental interferences has been established.2. A four-segment model of DF light response curve was proposed after analysis the characteristic of DF light response curves of different plant species. The four-segment form separates the light response curves to four different sections (UL, UC, S, and D section) according to characteristic. Based on the linear correlation between saturated light-induced DF intensity and Pn, and the four-segment form, a new method which is using unsaturated light-induced DF intensity to represent photosynthetic capacity is presented.3. The changes of DF dynamic decay signal and F730/F685 ratio of DF emission spectrum under heat stress have been researched. The veracity and effectiveness of detection plant heat stress response using the DF intensity and F730/F685 ratio was validated by comparative measurements of Pn with gas exchange technique.4. The experimental results show that different heat resistance plant has different temperature response curve of F730/F685 ratio. Moreover, a remarkable inflexion can be found on the temperature response curve of the plant which has worse heat tolerance. After analyzing the cause of the formation of inflexion on the temperature response curve of F730/F685 ratio, a new identification index of plant heat resistance has been presented.5. The response of DF intensity and emission spectrum of plant under salt stress, UV-B stress was carried out. For salt stress, effect of osmotic stress was mainly discussed. Comparative measurements of Fv/Fm, DF intensity and F730/F685 ratio of DF emission spectrum suggest that the degree of plant photosynthetic physiology damage whether caused by different concentration or different stress time can be effective measured by DF technique. For UV-B stress, a new method using DF signal and spectrum is proposed to detect the damage degree of plant induced by UV-B. The DF dynamic and spectral characteristics under different UV-B radiation time are investigated. After comparative measurements of Fv/Fm, DF intensity and F730/F685 ratio, the effectiveness of the DF technique used to rapid detect the UV-B stress damage degree is verified.In the end, summary of the whole work and the future work are made. |
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