Extraction of the Red Edge Position from Hyperspectral Reflectance Data for Plant Stress Monitoring

Remote sensing technique, based on hyperspectral reflectance measurements, is an alternative method with a great potential for plant monitoring and for more efficient crop management. Red Edge Position (REP), point of maximum slope on the reflectance spectrum of vegetation between red and near infrared (NER) spectral ranges is sensitive to chlorophyll (Chl) content and vegetation stress. In this study REP was extracted from hyperspectral reflectance data of two groups of young potato plants, healthy and infected with Potato Virus Y (PVY). Leaf reflectance data were collected by a portable fiber-optics spectrometer in the visible and NW spectral ranges with a spectral resolution of 1.5 nm. Four REP extraction techniques (maximum of first derivative, four-point linear interpolation, polynomial fitting, and inverted Gaussian modelling) were tested and compared. The results show that the wavelength and reflectance of REP for infected plants shift towards the shorter wavelengths in comparison with healthy plants that indicates the presence of a viral infection. The last three methods gave very close results for REPs (about 0.5 nm shift).