Research On Both Mechanism Of Delayed Fluorescence And Its Application In Agricultural Science

Delayed fluorescence (DF) associated with plant metabolism and photosynthesis.The mechanism and its applications in the agricultural science are presented in thethesis. Firstly, the primary common sense on DF and research progress wereintroduced in the chapter one, and then the basic concepts and locations ofphotosynthesis and the two photosystems were represented in the chapter two.Meanwhile, the concept and theory of delayed fluorescence are stated in detail.In the chapter three, a mathematical-physical analysis model, which describesindividually the electronic reflux of several significant components in thephotosynthesis electron transport chain, was developed. The process of electronsflowing back to the oxidized reaction center P₆₈₀⁺ was simulated by a series ofphotochemical reaction equations. Simulations based on this model showed that thedecay kinetics of DF accord with double exponential. DF components decaying in themillisecond range (fast phase) are related to the charge recombination of P₆₈₀⁺ and Q_A^-.The components decaying in the seconds range are associated with the recombinationof P₆₈₀⁺ with Q_B^2-.Based on the two-exponential model, the effects of DCMU on photosynthesis ofplant from the characteristics of DF decay kinetic curve and its total intensity wasstudied. All the results suggested that the fast phase of DF decay curve of leavesobviously rise after DCMU treatment, while the relative slow phase declined. Withthe different concentration DCMU treatment, the intensity of the DF and netphotosynthesis rate (Pn) behaved excellent correlation. Therefore, DF is an idealmarker to characterize the Pn of plant after DCMU treatment.In the chapter five, the effects of different kinds of herbicides on decay kinetics ofDF have been studied using a homemade portable DF detection system. The resultsdemonstrate that the analytic equation of DF decay dynamics we proposed can trulyand exactly reflect the mechanism and site about which herbicides inhibitphotosynthetic process. Therefore, DF decay dynamics may provide a practical and non-invasive means of pharmacology analysis of herbicides and damage-diagnosis ofphotosynthetic metabolism. It could be potentially useful for development of newgeneration herbicides.At the end of the paper, we have prospected the biological and medical applicationof delayed fluorescence. Finally, a full summary of the thesis is given.