Investigation of leaf biochemistry by statistics

The biochemical content (total proteins, cellulose, lignin, and starch) of about seventy plant leaves has been related to their optical properties through statistical relationships. Both fresh and dry plant material, leaves or needles, were used in this study. Stepwise multiple regression analyses have been performed on reflectance, transmittance, and absorptance values (individual leaves) as well as on infinite reflectance values (stacked leaves+needles), on rough values and on transformations of them such as the first derivative or the logarithm of the inverse reflectance. They underscored good prediction performances for protein, cellulose, and lignin with squared multiple correlation coefficients (R²) higher than 0.8 using ten wavelengths. Starch whose concentration in the leaf was smaller compared to the other components was retrieved with less accuracy. As expected, dry material and optically thick samples provided respectively better results than fresh material and individual leaves.