An algorithm for estimating chlorophyll content in leaves using a video camera

Plant leaf colour is commonly used as an index for nutrient diagnosis. We have developed a low-cost diagnostic method that is easy to use to assess the nutrient status of plants, based on the estimation of chlorophyll content of leaves using a portable colour video camera and a personal computer. Relationships between chlorophyll content and various functions derived from red, green and blue wavelengths are examined. Although red-blue and green-blue wavelengths show the highest correlation with chlorophyll content under a limited range of meteorological conditions, the normalized difference (red-blue)/(red + blue) is the most applicable function which can use data collected under different meteorological conditions. The accuracy in estimating chlorophyll content from video images could be improved by correcting with solar radiation data. It is shown that, for practical purposes, the chlorophyll content of leaves can be estimated with sufficient accuracy using a portable video camera. (C) 1998 Annals of Botany Company.