Spectral reflectance of rice seedlings

The spectral reflectance of young rice plants was measured in the visible and near-infrared region of the spectrum using a commercially available fiber optic contact probe and miniature spectrometer. This work aims to identify an empirical spectral index which changes when rice is exposed to increased levels of chloride anions in the irrigation water and soil. The ratio of near-infrared (lambda = 750 nm) reflectance to that of green (lambda = 555 nm), R-750/555, is known to be a quantitative measure of chlorophyll content in the leaf but in this study does not show a consistent shift for samples which are exposed to chloride levels equal to or less than 0.1% by mass of soil. However, leaf contact spectral reflectance measurements did reveal a significant and consistent increase in R-750/555 along the length of the leaves (in going from stem to tip), and this variation should represent an important factor in modeling remote and proximal sensing data.