NON-DESTRUCTIVE METHOD TO DETERMINING THE LEAF AREA IN HEMP, Cannabis sativa L.

Abstract

The evaluation of the leaf surface of hemp leaves, Cannabis sativa L., was the subject of the present study. The biological material was represented by the hemp variety 'Silvana', cultivated in SCDA Lovrin, Romania. Hemp leaves were taken randomly from mature plants. The leaves were herborized immediately after harvesting, in the field, in order to preserve the configuration of the leaves for analysis. Each leaf was scanned in a 1:1 ratio. The leaves were measured in terms of length (in the direction of the central leaflet) and width (maximum opening of the leaflets). For the measurement, a precision of ±0.5 mm was ensured. The scanned leaves were analyzed and the perimeter (Per) and scanned leaf area (SLA) were obtained. The correction factor (CF) was determined in order to be used for calculating the measured leaf area (MLA) by non-destructive methods. The value CF=0.27 was found, where the error as the difference between MLA and SLA (considered as a reference) was minimal (ME=0.87 cm2). The calculation of the RMSEP parameter confirmed the value of the correction factor (0.27), at which the RMSEP value was the minimum (RMSEP=9.74929). The fitting relationship between MLA and SLA was described by a linear equation, under conditions of R2=0.952, p<0.001. Polynomial equations of the 3rd degree described the interdependence relationship between SLA and parameters L (R2=0.932) and w (R=0.964) of the leaves, and a polynomial equation of the 2nd degree described the relationship between SLA and Per (R2=0.995). Stronger correlation levels were identified between MLA and dimensional parameters of leaves (L, w; r=0.969 for MLA with L; r=0.974 for MLA with w), than between SLA and dimensional parameters of hemp leaves (r =0.927 for SLA with L; r=0.957 for SLA with w). This difference can be explained based on the methods of determining SLA (by scanning) and MLA (by measurement, based on L, w, CF), MLA having a direct relationship between L and w from the calculation relationship, a fact that confirms the usefulness of the work method.