Trichome morphology of eleven genera of the tribeAlysseae (Brassicaceae)occurring in Bulgaria

Ančev, M. & Goranova, V.: Trichome morphology of eleven genera of the tribe Alysseae (Brassicaceae) occurring in Bulgaria. — Willdenowia 36 (Special Issue): 193–204. — ISSN 0511-9618; © 2006 BGBM Berlin-Dahlem. doi:10.3372/wi.36.36116 (available via http//dx.doi.org/)The leaf and silicule trichomes of 18 species of Alysseae were studied by scanning electron and light microscopy. Four trichome types are distinguished: (1) simple, (2) stalked 2- to 5-armed, (3) stellate and (4) dendritic trichomes. (1) Simple trichomes cover the leaves of Lunaria rediviva and, mixed with stalked 2- to 3-armed ones, compose the leaf indumentum of Camelina sativa. The simple trichomes on the silicules of Clypeola jonthlaspi subsp. microcarpa are columnar with transverse furrows. (2) Stalked 2-5-armed trichomes are present on the leaves of Draba korabensis, D. muralis, D. siliquosa and Erophila verna subsp. spathulata. Peculiar stalked trichomes with swollen globular base occur on the lower leaf surface of D. muralis. (3) Stellate trichomes cover the leaves of Alyssoides utriculata subsp. bulgarica, Aurinia saxatilis subsp. orientalis, A. uechtritziana and Clypeola jonthlaspi and the leaves and silicules of Alyssum cuneifolium s. str., A. orbelicum, A. pirinicum and Fibigia clypeata. (4) Dendritic trichomes co-occur with stellate ones on the silicules (but rarely on the leaves) of Berteroa species and Fibigia clypeata. The trichomes may be smooth (some stellate trichomes), minutely warty (simple and dendritic trichomes) or tuberculate (most of the stellate trichomes). The trichomes of the morphologically related species Alyssum pirinicum, a new combination validated here, and A. cuneifolium provide additional reliable features to distinguish them.