Histochemical Localization of Alkaloids in the Bulbs of In Vitro-Regenerated Snake’s Head Fritillary (Fritillaria meleagris L.): The Effect of a Temperature Regime

The genus Fritillaria is characterized by the production of alkaloids, primarily of the isosteroidal type. The aim of this preliminary study was to perform a histolocalization screening aimed at revealing the presence of alkaloids in the bulbs of F. meleagris, cultured in vitro under different growth regimes and at different developmental stages, as a powerful tool to identify preferable in vitro plant material for alkaloid isolation. Histochemical localization of alkaloids was performed using Wagner’s and Dragendorff’s reagents in fresh sections of bulbs cultured at 24 °C or 7 °C for 4 weeks, as well as those cultured at 24 °C following the 4-week chilling treatment, which were sampled at the beginning of sprouting. A positive reaction was observed with both reagents and was particularly intense in cold-treated bulbs. Alkaloids were mainly distributed in the bulbs and partly in the sprouts of the in vitro grown F. meleagris. The most intense staining, indicative of high alkaloid content, was observed in the bulb scales of pre-chilled bulbs that sprouted at 24 °C, rendering them preferable as in vitro plant material for alkaloid isolation. The results suggest that alkaloid production in the bulbs of F. meleagris can be improved by manipulating growth in the microenvironment of in vitro cultures, in order to meet the increasing industrial demand for medicinally or commercially important metabolites used as traditional medicines and herbal remedies.