Study on the trichomeS of the paraSitic weed broomrape: morphology and hiStochemiStry

Trichomes are epidermal hairs found on the aerial surfaces of nearly all plants and in different species. They grow in different shapes and act as protectors against insects, microbes and herbivores. Trichomes vary in their morphology, distribution pattern on a given organ and in their histochemical images. Different trichome types were observed in the aerial parts of the two species of broomrape (Orobanche aegyptica and Orobanche crenata), using both light and fluorescent microscopy techniques. Samples of the parasitic weed broomrape were collected from El-Aiat (Giza) and Helwan (South Cairo) in Egypt. Following standard methods, the samples were washed and prepared for light and epifluorescent microscopy. The examination revealed that the peduncles of both broomrape species were covered with trichomes. Their density varied according to their location on the peduncles. High trichome density was observed on the apex of broomrape peduncle. In the examined samples, all trichomes belonged to the multicellular uniseriate category and were classified as glandular and non-glandular types. Glandular trichomes were found to cover different parts of peduncles of the parasitic plant broomrape in both species, whereas non-glandular trichomes outgrew the corolla and anderoecium of O. aegyptiaca. On the other hand, crisped hairs were observed only on the anderoecium of both species. The histochemical tests showed positive reactions to lignin, phenolic, lipid and suberin materials in the outer layer of glandular trichomes, while the phenolic substances were detected in the neck cell and gland secreted cells.