Characteristic trichomes and indumentum specialization in African and European parasitic Scrophulariaceae.
Trichomes and their distribution patterns were observed in the aerial parts of plants of the genera Striga, Buchnera, Rhamphicarpa, Euphrasia, Melampyrum and Rhinanthus, using both light (LM) and scanning electron microscopy (SEM). All trichomes belong to the multicellular, uniseriate category and were classified as glandular and non-glandular types. On nearly all organs, the two types can be observed side by side. Apart from a large group of ubiquitous trichomes, some characteristic trichome types are reported; they are restricted either to chlorophyllous organs (foliage leaves, bracts, calyx and stem) or to the corolla. In some non-glandular trichomes mineral deposits were found. Other morphological and anatomical trichome features are discussed with regard to their possible function.