Leaf anatomy with emphasis on separation of two species of Varronia P.Br. (Cordiaceae) of the Brazilian semi-arid region

Abstract

This work points out some variations in leaf anatomy useful in the separation of two species of the genus Varronia P.Br., V. globosa Jacq. and V. leucocephala (Moric.) J. S. Mill., and some anatomical adaptations of the semiarid climate. These species differ in stomata distribution, types of glandular trichomes, non-glandular trichomes density, accumulation of substances in V. leucocephala, crystal types, colenchyma type in midrib and petiole, and the vascular bundles in petiole. As unifying characters, both have uniseriate epidermis, glandular and non-glandular trichomes, dorsiventral leaves, crystals, collateral vascular bundles in leaf blades, and petiole with three vascular traces. The morphological study of trichomes has been extensively explored since it is one of the main characteristics differing the species from the genus, and being recognized several types of glandular trichomes, particular to each species. Some anatomical typical features of plants occurring in xeric environments were also identified: stomatal distribution, abundant trichomes with micropapillae on its surfaces, and lipid accumulation.