In the aroma emitted from the RR callus, exposure to the same type of UV radiation caused very different effects on the eugenol and methyleugenol production. In fact, the eugenol and methyleugenol levels were especially increased by the exposition at UV-B WG 305 nm exposure for 6 h (7% and 9%, respectively), while the same radiation used for 3 h inhibited generally their biosynthesis (Table 4b).