The assessment of reflectance ratios for determination of water content in leaves using shorter end of near-infrared spectroscopy

Leaf water content is essential to measure the growth of plants and estimate the risk of drought or forest fire. Scientists have shifted their attention from conventional methods to spectroscopic techniques, as they can provide real-time water monitoring in plants from a remote accessed station. In the study, data were acquired from oven-dried leaves at various stages of heating. The correlogram between reflectance intensity and equivalent water thickness against wavelengths was used to identify the suitable wavelengths and associated reflectance ratios for further assessment of water content in the leaf. Based on the nature of acquired data, exponential and bi-exponential models were applied to relatively evaluate the optimal reflectance ratios for the determination of water content in leaves. Moreover, the results were compared with the water index (WI) reflectance ratio (R-900/R-970) and the three-band ratio index (RATIO(975) ).The WI reflectance ratio is typically used as a standard estimator of water content in plants while RATIO(975) is another suitable three-band ratio centered at 975 nm gaining wide acceptance. The observation in the study might be useful in finding the optimal indices for the qualitative assessment of leaf water content within the shorter range (600-1100 nm) of near-infrared spectroscopy.