Leaf anatomy of Vriesea (Tillandsioideae–Bromeliaceae).

The Bromeliaceae are a largely Neotropical family originating in open, dry environments. Vriesea Lindl., the third largest genus of the family, is traditionally divided between two sections. About 90% of the species of the genus occur in Brazil, where the centre of diversity is the Atlantic Rainforest. Leaf morphoanatomical studies conducted on bromeliad species have confirmed the importance of structural characters for ecological, and also for systematic purposes. Because of the wide morphological, ecological and taxonomic diversity of Vriesea, and its importance in ecosystems associated with the Atlantic Rainforest, we selected 24 Vriesea species and used anatomical and histochemical analyses to describe the leaf anatomy aiming to identify potential systematic characters, and point out possible traits that responded to environmental conditions during the evolution of the genus. The leaves are hypostomatic with peltate trichomes. They present epidermis with thickened cell walls, with lignin and pectin, covered by cuticle and epicuticular wax. The mechanical hypodermis is usually one-layered. Water-storage parenchyma occurs in both surfaces of the leaf blade. The chlorenchyma is located in the median portion of the blade. Air lacunae are associated with brachiform parenchyma. The vascular bundles are collateral, arranged alternately with the air lacunae and surrounded by a sheath of sclerified and/or parenchyma cells. Extravascular fibres occur in most of the species and are positioned below the mechanical hypodermis on the adaxial surface of the leaf blade. Leaf anatomical analysis can be useful in differential characterisation of small groups of related species but does not seem to reflect species assemblages according to the taxonomic sections or substrate type, but is consistent among the Brazilian analysed species of Vriesea. [ABSTRACT FROM AUTHOR]