Retrieval of betalain contents based on the coupling of radiative transfer model and SVM model

•Simulating canopy reflectance using PROSAIL model.•Hyperspectral indices NDSI473nm, 475nm, RSI473nm, 475nm and NDPI473nm, 475nm are sensitive to the Betalain contents.•Carrying out spectral conversion to invert Bt content at multispectral level. Betalain (Bt) is as a class of edible natural pigments and important biochemical aparmeter can explain the physiological response and the resistance of plants caused by different environmental stress factors. Hyperspectral spectroscopy has been widely used to estimate plant pigments contents accurately and non-destructively. However, there is very little research about hyperspectral remote sensing estimation and inversion of betalain contents. The algorithm of Bt content inversion with viable universality is the key to improving the practicality of quantitative remote sensing. Therefore, in this study, based on the radioactive transfer mechanism and SVM model, the optical characteristics of Bt and other factors of Suaeda salsa are analyzed, and a coupling model (PROSAIL + SVM) of simulated canopy reflectivity and factor contents is established. The model was then applied to the remote sensing inversion. Results demonstrated that Bt content was sensitive to the spectral range between 460 and 592 nm, particularly between 530 and 550 nm where the sensitivity index reached 0.7. Optimized indices; NDSI473nm,475nm, RSI473nm,475nm and NDPI473nm,475nm, calculated by simulated spectral reflectance had a significant correlation with Bt content (R= ±0.80, p