Imaging Spectroscopic Characteristics And SPAD Value Estimation Modeling Of Three Kinds Of Leaf Leaves Of Rapeseed

The material basis of rapeseed yield is mainly from photosynthesis.The green photosynthetic area of rapeseed determines the yield of rapeseed.The photosynthetic area of rapeseed includes leaf area and pod area.The former is mainly used for the growth of rapeseed plants,while the latter contributes about 70% to the yield of rapeseed.Therefore,it is of great significance to study the leaf and pod of rapeseed related to photosynthesis.In this paper,the long petiole leaf,short petiole leaf and no petiole leaf of rape were studied.The spectral characteristics and chlorophyll content of three kinds of rape leaves were measured by imaging hyperspectral technology and principle,and SPAD-502 chlorophyll meter.The imaging spectral characteristics of three kinds of rape leaves in darkroom were obtained.The differences of spectral characteristics of three kinds of rape leaves were analyzed,and the relationship model between plant index(NDVI)and SPAD value was established.The purpose of the model is to use crop hyperspectral technology to obtain non-destructive growth parameters of rapeseed,and to monitor rapeseed growth effectively,so as to provide an alternative method for traditional destructive sampling methods.The experimental results show that:(1)The hyperspectral curves of three kinds of leaves(long petiole leaf,short petiole leaf and no petiole leaf)of rape in different periods were basically the same,and had obvious common law.According to the statistical analysis of SPAD value,it was found that the chlorophyll content of short petiole leaf was higher than that of long petiole leaf at low temperature bolting stage,and that of non-petiole leaf was higher than that of long petiole leaf and short petiole leaf at high temperature and precipitation flowering stage.(2)The hyperspectral curved shape and change rule of the same rape leaf in different phenological periods are basically the same,but there are some differences between different periods.The reflectivity of long petiole leaf is slightly higher at seedling stage than at bolting stage and flowering stage,and that of short petiole leaf is slightly higher at bolting stage than at flowering stage.Statistical analysis of SPAD value showed that the chlorophyll content of long petiole leaf and short petiole leaf was the highest at bolting stage and that of petiole leaf was the highest at Seedling Stage under the combined influence of temperature,rainfall,light intensity and plant location.(3)In this study,each vegetation index is used as feature extraction method,and SPAD value estimation model is built by combining linear regression and support vector machine.The results show that the SPAD value estimation model based on support vector machine is better than the SPAD value estimation model based on single regression.The fitting determination coefficient R is close to 1,and the root mean square error and relative error are equal.For the smallest,the accuracy of the model is higher.It is the best model for estimating SPAD of three rapeseed leaves.