Glandular trichomes of Calceolaria adscendens Lidl. (Scrophulariaceae): histochemistry, development and ultrastructure

This paper reports the results of a study of the morphology and development of glandular trichomes in leaves of Calceolaria adscendens Lidl. using light and electron microscopy. Secretory trichomes started as outgrowths of epidermal cells ; subsequent divisions gave rise to trichomes made up of a basal epidermal cell, a stalk cell and a twocelled secretory head. Ultrastructural characteristics of trichome cells were typical of terpene-producing structures. Previous phytochemical studies had revealed that C. adscendens produces diterpenes. Comparison with C. v olckmanni, which produces triterpenes, and has trichomes with eight-celled secretory heads, suggests that there could be a relationship between the type of glandular trichome and the class of terpene produced. Further work is needed to test the hypothesis and to develop trichome characters as taxonomic tools.