The effects of sulphur dioxide on the spectral curves and chlorophyll concentration of rice canopy

Abstract

This experiment investigated the relationship among the reflectance spectral vegetation indices, sulphur dioxide (SO2) concentration and chlorophyll concentration (Ch) of rice canopy under different levels of atmospheric SO2. A split plot field experiment comprising seedlings of three genotypes of rice was exposed to SO2 at different concentrations. Visible and near infrared canopy reflectance were measured for each SO2 treatment 30 days and 46 days after transplanting, respectively. SO2 concentration had a strong negative relationship with Ch-a (chlorophyll-a concentration), Ch-b (chlorophyll-b concentration) and Ch-t (total chlorophyll concentration) (correlation coefficients R from −0.454 to −0.618) at the 0.01 confidence level. Green and red reflectance varied with SO2 concentrations. Average reflectance were used to calculate difference vegetation index (DVI), normal difference vegetation index (NDVI) and ratio vegetation index (RVI). MERIS Terrestrial Chlorophyll Index (MTCI) was used in this investigation also. One-sample tests showed that for this spectral laboratory there was significant difference at the 0.01 level at those vegetation index (DVI, RVI, NDVI and MTCI). DVI (ρred–ρgreen, ρnir–ρred and ρnir–ρgreen), NDVI (ρnir–ρred/ρnir+ρred), RVI (ρnir/ρred) and MTCI were significantly correlated with Ch-b, and Ch-t at the 0.05 confidence level or above. Although MTCI was significantly correlated with Ch-b and Ch-t, it was not strongly correlated with SO2 concentration. DVI, NDVI (ρnir–ρred/ρnir+ρred) and RVI (ρnir/ρred) were proved effective methods to estimate the injury of rice by SO2 air pollutant.