Non-destructive detection of water stress and estimation of relative water content in maize

Non-destructive estimation of leaf water content provides vital information about vegetation productivity. We report here on controlled seven day experiments using greenhouse-grown maize. Fifty plants were randomly assigned to two equal groups: water stressed and well watered. Spectroscopic, relative water content (RWC), and chlorophyll concentration measurements were made daily. Because water molecules absorb radiation in near- and middle-infrared, most efforts to sense water deficit remotely utilize infrared wavelengths. In these experiments, we identified a strong, systematic, and repeatable relationship between photosynthetically active radiation (PAR, 400700 nm) albedo and leaf RWC. We show that visible spectrum reflectance provides a means to detect early stages of plant stress and estimate leaf RWC.