ESTIMATION OF CHLOROPHYLL CONTENT OF LEAVES USING REFLECTANCE MEASUREMENTS OR DIGITALIZED PHOTOGRAPHS OF LEAVES TAKEN IN THE LABORATORY

A simple method based on model simulations of leaf reflectance was proposed for the estimation of leaf chlorophyll content from reflectance measurements in the red or green parts of the spectrum. The results were evaluated with sugar beet leaves using 2 methods to acquire the data. The methods were chosen for their ability to provide measurements on large samples: first, direct measurements of leaf reflectance were made using a photographic densitometer capable of taking quick measurements on small areas (5 mm2). Second, indirect estimates of leaf reflectance were made from digital analysis of color photographs of leaves taken in laboratory; this gave an image of the spatial distribution of pigments. Experimental results confirmed that a simple relation exists between reflectance and chlorophyll content. However, the experimental parameters of the relation significantly differed from those computed from the model ft seems that the difference is mainly due to the use of broad band sensors. Thus for operational use, it is necessary to calibrate 2 parameters on a sample of leaves of known chlorophyll content.