The relative chlorophyll content (SPAD value) and % N were determined by means of SPAD-502 chlorophyll
meter (Konica Minolta, Japan) and nitrogen meter Agriexpert CCN 6000 (Satake, Japan), respectively. The adaxial
side of the leaves was always placed toward the emitting window of the instrument and major veins were avoided.
Each leaf, based on its total leaf area, was marked in five up to 14 representative points for in vivo measurements,
and the average value was calculated. As for basil, due to its small size, seven leaves were used with two up to three
spots of measurement each. This method was intended to overcome the influence of non-uniform distribution of
chlorophyll in the leaf, and hence producing more representative data.