A Study On The Modeling And Regulation Of Plant Photosynthetic Activities Based On Chlorophyll Fluorescence

Photosynthesis is the material source for all life activities on the earth,and the energy basis of human activities.The growth of crops in agricultural production is the result of the accumulation of products formed by absorbing light energy through the mechanism of photosynthesis.In the face of the shortage of land resources and the increasing population,greenhouse plays a vital role in modern agriculture,because it allows artificially controlling environmental factors.At present,the environmental control strategies of greenhouses do not depend on the physiological real-time demand of crops,but more on the farmer experience.Plant growth control is one of the future trends in the interdisciplinary field of botany and automation.It is one of the 125 global problems published in the Science maganize.The chlorophyll fluorescence released by plant photosynthesis is coupled with photosynthesis and easy to measure,so a model on photosynthesis based on chlorophyll fluorescence is very important.Based on the theory and method of system modeling,this thesis studies the modeling of photosynthesis based on chlorophyll fluorescence from the viewpoint of energy and electron transfer in plant photosynthesis.1.Modeling the whole process of light-dark reactions in photosynthesis.According to photosynthetic electron transfer and biochemical reaction activities in the dark and light and reaction stages,a mathematical model of photosynthesis based on differential equations was established.The parameters of the model are identified by using the Levenberg-Marquardt algorithm.The results show that the output signal of the model is in good agreement with the experimental chlorophyll fluorescence data,and the average relative fitting error is 0.028%.2.Physiological regulation strategy research based on the photosynthetic model.Aiming at the difficulty of measuring the intermediate state in photosynthesis system and the errors in modeling or measuring process,the extended Emmerich Kálmán technique(EKF)is used to estimate the intermediate state of products based on the measurable chlorophyll fluorescence,for example,the amount of carbohydrate produced is controlled by neural network PID algorithm,and chlorophyll fluorescence is used as feedback signal to regulate photosynthesis.The results show that the reduction efficiency of PQ in photosynthesis mechanism can be controlled based on chlorophyll fluorescence as feedback signal.It provides a basis for the optimal control of photosynthesis in future,and provides a potential solution to the problem of greenhouse regulation based on real-time plant physiological needs.3.Modeling and optimization of photosynthesis photoreaction process as affected by both light intensities and temperatures.Light intensity and temperature are the most important environmental factors affecting photosynthesis of greenhouse plants.The modeling of Photosynthesis System II with light intensity and temperature as input parameters is studied.The model describes the effect of temperature on photosynthesis according to the Arrhenius equation,and uses chlorophyll fluorescence as the measureable signal.The validity of the model in simulating the effects of light intensity and temperature on photosynthesis was verified by comparing the output of the model with the experimental data of chlorophyll fluorescence.Aiming at the multi-environmental factors of light intensity and temperature,the application of the group optimization algorithm in the optimization of photosynthesis was studied.Through the establishment of a photosynthesis benefit function,the particle swarm optimization algorithm was used to find the best solution under different environmental conditions,which confirmed the unique advantages of the swarm particle algorithm in the optimization process.This provided a basis for further control of crop photosynthetic activities.This study is an original interdisciplinary research,which contributies to the solution of one of the 125 global problems published in the Science magazine.It has important theoretical value and practical significance for greenhouse crop modeling and regulation.