4.4. Histochemical Analyses

Fresh free-hand sections of corollas containing glandular and non-glandular trichomes as well as fragments of stamens were subjected to histochemical assays. The following specific reagents were used for detection of the presence of substances: Sudan III (POCH, Gliwice, Poland) [136], Sudan Red B (POCH, Gliwice, Poland) [137] (pp. 874–928) [138], and Sudan Black B (POCH, Gliwice, Poland) [139] for total lipids, Nile Blue (POCH, Gliwice, Poland) for neutral and acidic lipids [140,141], Nadi reagent (POCH, Gliwice, Poland) for terpenes and essential oils [142], Neutral Red (POCH, Gliwice, Poland) for terpenoids (essential oils) [143,144], and Godin reagent (vanillin—sulfuric acid) (POCH, Gliwice, Poland) for iridoids [145]. Six trials/replicates were performed for each reagent. Fresh unfixed and unstained sections of corollas and fragments of stamens were used as a negative control. Photographic documentation was made using a Coolpix 4500 (Nikon) camera coupled to an Eclipse 400 (Nikon) light microscope.