Foliar area measurement by a new technique that utilizes the conservative nature of fresh leaf surface density

Leaf-area (LA) is a plant-biometric index important to agro-forestry and crop production. Previous works have demonstrated the conservativeness of the inverse of the product of the fresh leaf’s density and thickness the so-called ‘Hughes’ constant’ (K). We use this fact to develop ‘LAMM’, an absolute method of LA measurement (i.e. no regression fits or prior calibrations with planimeters). Nor does it require drying the leaves. The concept involves the in situ determination of K using geometrical shapes and their weights obtained from a sub-set of fresh leaves of the set whose areas are desired. Subsequently the LAs (at any desired stratification level), are derived by utilizing K and the previously measured masses of the fresh leaves. The concept was first tested in the simulated ideal case of complete planarity and uniform thickness by using plastic-film covered card-paper sheets. Next the species-specific conservativeness of K over individual leaf zones and different leaf types from leaves of plants from two species, Mandevilla splendens and Spathiphyllum wallisii, was quantitatively validated. Using the global average K values, the LA of these and additional plants, were obtained. LAMM was found to be a rapid, simple, economic technique with accuracies, as measured for the geometrical shapes, that were comparable to those obtained by the planimetric method that utilizes digital image analysis (DIA). For the leaves themselves, there were no statistically significant differences between the LAs measured by LAMM and by the DIA and the linear correlation between the two methods was good (R = 0.99).