Leaf Nitrogen Analysis of Poinsettia (Euphorbia Pulcherrima Will d.) Using Spectral Properties in Natural and Controlled Lighting

Studies of spectral properties were performed on living poinsettia foliage and subjected to four different nitrogen treatment levels. Studies were conducted in both a greenhouse and growth chamber. Low-nitrogen plants grown in both greenhouses and growth chambers showed similar increases in red reflectance (0.7-0.75 mm), but had different levels of near-infrared reflectance, due to different amounts of plant canopy cover. Statistical results showed that red reflectance could discriminate between 0 ppm nitrogen treatments and higher nitrogen treatments. Near-infrared reflectance was found related to the amount of plant material exposed relative to the amount of other background surfaces. The normalized difference index provided the best method of discriminating nitrogen-deficient plants.