Simulation And Analysis Of Photosynthetic Rate Of Tomato Leaves In Solar Greenhouse

Photosynthesis is an important link in crop growth and yield formation.Because the crop environment in solar greenhouse is controllable to a certain extent,quantitative understanding of photosynthesis and its regulations affected by environmental factors is of great significance for rational regulation of greenhouse microclimate and improvement of crop production efficiency.Simulation model is an important way to achieve this goal.For this reason,the photosynthetic rate of tomato leaves and its related factor parameters in solar greenhouse were measured in situ by Li-6800 portable photosynthetic instrument in Raoyang county,Hengshui,Hebei Province.With assumed non-water stress situation,which is the case of the experiment field,three photosynthetic models were established by integrating photosynthetic effective radiation（PAR）,air temperature and CO₂ concentration onto three common light response models,i.e.,right angle hyperbola model,index model and non-right angle hyperbola model.The model parameters were determined by mountain climbing method.Through the test and verification analysis of the simulation results,the improved right angle hyperbola model with the best simulation effect and its parameters are finally taken as the working model of this paper.Based on this improved right angle hyperbola model,the variation of the tomato leaf photosynthetic rate in greenhouse and the diurnal pattern of microclimatic environmental factors impacting on leaf photosynthetic rate were analyzed quantitatively.Based on these modelling results,some suggestions were put forward for greenhouse management from the perspective of leaf photosynthetic rate of greenhouse crops.The main research conclusions are as follows:（1）Determined the improved right-angle hyperbolic photosynthetic model as qualified and best model tool for tomato photosynthesis simulation in greenhouse condition.The correlation coefficients between the simulated results and the measured values by back-substitution and verification are R²=0.8213 and R²=0.8244,respectively（p<0.01）.Compared with the measured data,the simulation results have higher accuracy.（2）The established photosynthetic model is able to estimate the photosynthetic rate in greenhouse by using other microclimate data.（3）The photosynthesis reached the peak value from 10:00 AM to 11:00 AM,and decreased at noon,then reached another smaller peak at around 2:00 PM,but was significantly lower than the before-noon peak.The established photosynthetic model includes three environmental elements（light,temperature and CO₂ concentration）,which can simulate the noon pattern phenomenon.Through modelling analysis,the main reason for this phenomenon are the decrease of CO₂ concentration and the extremely high-temperature stress in the greenhouse at noon time,which has an inhibitory effect on photosynthesis of plants.（4）From the perspective of leaf photosynthesis,the greenhouse coversheet should be open earlier,like simultaneously when sunrises,when the weather is good,the best use the aerly morning sunlight when air temoerature is just perfect for photosynthesis to improve cropgrowth;After 4PM every day,due to the very weak PAR,the photosynthetic rate is very low,so the greenhouse coversheet could be closed in time,to maintain the temperature in the greenhouse.