Modeling And Effect Analysis Of Multiple Environmental Factors On The Growth Of Melon And Lettuce Seedlings

Industrialized seedling production is a way of mass production of plants by using modern scientific and technological means and advanced equipment.The most critical factor in seedling is environmental regulation.There are complex interactions between different environmental factors,and it is difficult to achieve the ideal regulation effect through the regulation of a single factor.In order to explore the impact of multiple environmental factors coupling on horticultural crops,analyze the interaction between multiple environmental factors,find the best combination of environmental factors,and provide scientific basis for environmental regulation in factory seedling growing.In this study,melon and lettuce were used as experimental materials,daytime air temperature,CO₂ concentration and nutrient solution concentration were used as regulatory factors,and the three-factor and five-level universal rotating combination design was used.Firstly,the influence of environmental factors on single index was analyzed.Then the factor analysis method was introduced to extract the common factors of six growth indicators（total fresh weight,total dry weight,net photosynthetic rate,seedling index,leaf area and chlorophyll content）,and the obtained common factors were used as the comprehensive evaluation index of seedlings.On the basis of this experiment,the light response curve of different treatments was measured,and the Support vector Machine（SVR）algorithm was used to construct the prediction model of net photosynthetic rate.Based on the model,the effects of light intensity,daytime air temperature,CO₂ concentration and nutrient solution concentration on the net photosynthetic rate of the two kinds of seedlings were analyzed.The photosynthetic rate prediction model was used to predict the light response curve under different environments,and the point with the maximum curvature on the response curve was used as the light intensity control point under different environments.Finally,the optimal control light intensity prediction model was constructed by taking three environmental factors as input and the optimal control light intensity as output.The main results and conclusions are as follows:it has the characteristics of strong spatial closure,high degree of environmental regulation and small influence by the external environment,can be continuous production,can improve the seedling efficiency,shorten the seedling cycle,and improve the success rate of seedling.The most critical factor in seedling is environmental regulation.There are complex interactions between different environmental factors,and it is difficult to achieve the ideal regulation effect through the regulation of a single factor.In order to explore the impact of multiple environmental factors coupling on horticultural crops,analyze the interaction between multiple environmental factors,find the best combination of environmental factors,and provide scientific basis for environmental regulation in factory seedling growing.In this study,melon and lettuce were used as experimental materials,daytime air temperature,CO₂ concentration and nutrient solution concentration were used as regulatory factors,and the three-factor and five-level universal rotating combination design was used.Firstly,the influence of environmental factors on single index was analyzed.Then the factor analysis method was introduced to extract the common factors of six growth indicators（total fresh weight,total dry weight,net photosynthetic rate,seedling index,leaf area and chlorophyll content）,and the obtained common factors were used as the comprehensive evaluation index of seedlings.On the basis of this experiment,the light response curve of different treatments was measured,and the Support vector Machine（SVR）algorithm was used to construct the prediction model of net photosynthetic rate.Based on the model,the effects of light intensity,daytime air temperature,CO₂concentration and nutrient solution concentration on the net photosynthetic rate of the two kinds of seedlings were analyzed.The photosynthetic rate prediction model was used to predict the light response curve under different environments,and the point with the maximum curvature on the response curve was used as the light intensity control point under different environments.Finally,the optimal control light intensity prediction model was constructed by taking three environmental factors as input and the optimal control light intensity as output.The main results and conclusions are as follows:1.The main factor effect,single factor effect and marginal effect of environmental factors on the net photosynthetic rate,seedling index and leaf area of melon and lettuce seedlings were clarified.Daytime air temperature was the main regulator of net photosynthetic rate and leaf area of melon seedlings,and nutrient solution concentration was the main regulator of seedling index.In the single factor effect analysis,the effects of net photosynthetic rate and leaf area on daytime air temperature,CO₂ concentration and nutrient solution concentration were parabola under the opening line,and the effects of the three factors on seedling index were monotone increasing curve.In the marginal effect analysis,the three factors had negative effects on net photosynthetic rate and leaf area,daytime air temperature had negative effects on seedling index,and CO₂ concentration and nutrient solution concentration had positive effects on seedling index.Daytime air temperature was the main regulator of net photosynthetic rate and leaf area of lettuce seedlings,and nutrient solution concentration was the main regulator of seedling index.In the single factor effect analysis,the effects of the three factors on net photosynthetic rate and leaf area were all open downward parabola,the effects of strong seedling index on daytime air temperature were monotone increasing curve,and the effects of CO₂ concentration and nutrient solution concentration were open downward parabola.In the marginal effect analysis,the three factors have negative effects on the three indicators.2.Analyzed the effects of the interaction of multiple environmental factors on the comprehensive growth indicators of the two cropsBased on the response model,the interaction of the three factors within the test range was determined.Under different daytime air temperatures,the synergistic effect of appropriate CO₂ concentration and nutrient solution concentration can promote the growth of melon and lettuce seedlings.The effect of daytime air temperature on melon seedlings was greater than that of CO₂ concentration and nutrient solution concentration under different CO₂concentration and nutrient solution concentration.The influence of nutrient solution concentration on lettuce at different temperatures was greater than that of CO₂ concentration.At different concentrations of CO₂ and nutrient solution,daytime air temperature had a greater effect on lettuce seedlings.The suitable range of air temperature was 33℃～35℃,the suitable range of CO₂concentration was 1 043～1 408μmol/mol,and the suitable range of nutrient solution concentration was 2.4～2.6 m S/cm.The suitable range of air temperature was 26℃～28℃,the suitable range of CO₂ concentration was 1 215～1 456μmol/mol,and the suitable range of nutrient solution concentration was 1.7～2.0 m S/cm.3.The response model of net photosynthetic rate of two kinds of seedlings to light intensity,daytime air temperature,CO₂ concentration and nutrient solution concentration and the prediction model of optimal control light intensity were constructed.A total of 315 sets of experimental data of melon seedlings and 420 sets of experimental data of lettuce seedlings were obtained by measuring the light response curve data of melon seedlings and lettuce seedlings,respectively.The data samples were divided into training set and test set at a ratio of 7:3.The support vector machine algorithm was used to establish the prediction model of net photosynthetic rate.The net photosynthetic rate under different environmental combinations was calculated by the photosynthetic rate prediction model,and the optimal control light intensity under the combination of three environmental factors was calculated by the maximum curvature value method.1331 sets of data were obtained for each crop,and the data samples were divided into 7:3.The support vector machine（SVM）algorithm was used to establish the optimal control light intensity prediction model for melon seedlings and lettuce seedlings.The results showed that R2 on the test set was 0.933 and 0.886,respectively.According to the model,the optimal light intensity for melon seedlings was 867μmol/（m²·s）under suitable daytime air temperature,CO₂ concentration and nutrient solution concentration.The optimum light intensity was 674μmol/（m²·s）under the suitable daytime air temperature,CO₂ concentration and nutrient solution concentration for lettuce seedlings.