Notes on the cuticular ultrastructure of six xerophytes from southern Africa

Cuticular ultrastructure of six perennial xerophytes from the arid winter rainfall region of Namaqualand in southern Africa was examined and their structural significance was discussed from an ecological perspective. They included taxonomically unrelated species namely Antizoma miersiana Harv. (Menispermaceae), Hermannia disermifolia Jacq. (Sterculiaceae), Rhus burchelli Sond. ex Engl. (Anacardiaceae), Galenia africana L. (Aizoaceae), Eriocephalus ericoides (L.f) Druce (Asteraceae) and Diospyros ramulosa (E. Mey. ex A. DC.) De Winter (Ebenaceae). The leaves of five species were characterized by thin cuticles. The outer periclinal cell walls of the epidermal cells were uncutinized, except in Antizoma miersiana. According to differences in ultrastructure, six different cuticular types were identified, ranging from various classes of reticulate, lamellate and homogenous types. One species (Galenia africana) has an unusually osmiophilic cuticle, delimited from the cell wall by an electron-lucent zone. No conclusion could be made regarding the association between xerophytism and a specific cuticle type.