  Leaf area LA, is a plant biometric index important to agroforestry and crop
production. Previous works have demonstrated the conservativeness of the
inverse of the product of the fresh leaf 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
subset 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 excellent.
