Fig. 2. The trends of changes in pigment specific simple ratio-chlorophyll-a (PSSRa), ratio analysis of reflectance spectra-chlorophyll-b (RARSb), and ratio analysis of reflectance spectra-carotenoids (RARSc) with the changes of values of SPAD in three different growth stages. Boot, Hd, and GF indicate the measurements were taken at booting, heading, and grainfilling.