Chlorophyll Content Analysis Of Oilseed Rape Leaves Based On A Single Integrating Sphere Measurement System Coupled With An Inverse Strategy

Leaf chlorophyll content is an important indicator of crop growth status.How to quickly and accurately obtain chlorophyll content is of great significance for crop growth monitoring,stress analysis and estimation.In view of the current poor accuracy and low efficiency of chlorophyll content prediction,this paper constructed a single integrating sphere measurement system platform based on the demand of chlorophyll inversion of rapeseed leaves,and selected random forest model and PROSPECT model to explore the optimal strategy of chlorophyll inversion.The main research contents were as follows:(1)Based on the data of ANGERS database,the effects of different inversion strategies on chlorophyll prediction or inversion were preliminarily determined:based on ANGERS database,different spectral bands,different spectral properties:reflectance,transmittance,reflectance+transmittance,different inversion and prediction models for chlorophyll content prediction or inversion were compared,The results showed that the optimization of the chlorophyll inversion of 400-1000 nm was preferred for both the random forest model and the PROSPECT model.(2)A single integrating sphere detection system platform was constructed:a measurement system platform suitable for measuring the hemispherical reflectance and hemispherical transmittance of rapeseed leaves 400-1000 nm was constructed,and 5 different concentrations model samples were prepared based on 20%Intralipid solution and Blue dye power.With reference to the standard,the theoretical absorption coefficient?_a and the reduced scattering coefficient?_s'are calculated.Then,based on the hemispherical reflectance and hemispherical transmittance measured by the integrating sphere,the IAD algorithm was used to calculate the absorption coefficient?_a and the reduced scattering coefficient?_s'.Comparing the calculated values obtained from the experiment with the theoretical values,the results showed that the system reliability was good and can be used for subsequent experimental measurements.(3)Based on the chlorophyll inversion of different spectral properties of the single-precision sphere measurement system PROSPECT model,the R~2 values of the chlorophyll correlation and the measured chlorophyll correlation analysis of the reflectance,transmittance,reflectance+transmittance inversion at 400-1000 nm were 0.65,0.82,0.83,respectively;the RMSE values were 5.13?g/cm ~2,3.57?g/cm ~2,and 3.31?g/cm ~2,respectively.Based on the chlorophyll inversion results of different spectral properties of the random forest model of the single integrating sphere measurement system,the R~2 values of the chlorophyll correlation and the measured chlorophyll correlation analysis of the 400-1000 nm reflectance and transmittance model set inversion were 0.88 and 0.90,respectively.The results of the RMSE values were 1.46?g/cm~2,1.33?g/cm~2,respectively.The reflectance of the 400-1000 nm reflectance set and the R2values of the chlorophyll correlation analysis of the measured chlorophyll correlation were 0.76and 0.80,respectively;The values of the values are 3.34?g/cm ~2 and 3.30?g/cm ~2,respectively.Based on the PROSPECT model and the chlorophyll inversion results of different periods of the random forest model based on the single integrating sphere measurement system,based on the PROSPECT model,the R~2 values in different periods are 0.83,0.89,0.78,0.79,and 0.89,respectively;the RMSE values are 2.24,respectively.?g/cm~2,1.82?g/cm~2,2.72?g/cm~2,2.98?g/cm~2,1.95?g/cm~2.Based on the random forest model,the R~2 values for different periods were:0.14,0.84,0.54,0.45,and 0.60;the RMSE values were 2.24?g/cm~2,1.82?g/cm~2,2.72?g/cm~2,2.98?g/cm~2,and 1.95,respectively.Based on the chlorophyll inversion results of different bands of random forests in ASD portable field spectrometer,the R2 values of chlorophyll correlation and chlorophyll correlation analysis of 400-1000 nm and 400-2500 nm reflectance model set were0.91 and 0.91,respectively.The RMSE values were 2.40?g/cm~2 and 1.71?g/cm~2,respectively.The R~2 values of the chlorophyll correlation and the measured chlorophyll correlation analysis of the reflectivity prediction set inversion of 400-1000 nm and 400-2500 nm were 0.58 and 0.52,respectively.The results of the RMSE values were 5.21?g/cm~2 and 5.62?g/cm~2,respectively.The above results showed that based on the single integrating sphere measurement system,the strategy of chlorophyll inversion using the reflectance of the PROSPECT model 400-1000 nm was optimal.