Estudo comparativo do xilema secundário de espécies de Urbanodendron Mez e contribuição da anatomia do lenho à taxonomia da família Lauraceae Juss

Abstract

Lauraceae Juss. is a pantropical and economically important plant family, consisting of 50 genera and approximately 3,000 species, mostly found in humid forests. Several species are important resource in the construction timber, spice, essential oil, and medicinal plants. Among the 22 genera of Lauraceae occurring in Brazil, Urbandodendron Mez. is a genus with three species found in Southeastern Brazil and in Bahia state. Due to the complexity of that group, several classification systems have been proposed to the family. The most recent system suggests the division of the Lauroidea subfamily into three tribes, based on inflorescence morphology and on characters of wood and bark anatomy. On the other hand, Urbanodendron has not been included in that classification, since there are no studies on wood anatomy for that genus up to date. This study aims to provide information that can support Lauraceae taxonomy by describing wood characters of Urbanodendron bahiense (Meisn.) and U. verrucosum (Ness) Mez., followed by a literature review on the wood anatomy of other 21 genera of Lauraceae. Wood samples of both species were collected with an increment borer and processed based on usual techniques of optical and scanning electron microscopy. In order to verify if environmental factors may affect wood structure, samples were collected in Lowland and Submontane Ombrophilous Dense Forest remnants located in two conservation units in Rio de Janeiro state, the Parque Natural Municipal do Curió and the Reserva Biológica de Poço das Antas. A Principal Coordinates Analysis (PCoA) was used to evaluate how wood anatomy characters may support an intrafamiliar diagnosis in Lauraceae. The comparative analysis between the wood anatomies of U. bahiense e U. verrucosum indicated a homogeneous wood structure for both species, as observed in the other genera of Lauraceae, showing the following wood anatomical characters: growth ring boundaries distinct; porosity diffuse, solitary vessels and radial multiplex of 2-4, circular to oval outline, exclusively simple perforation plates, alternate intervessel pits; septate fibre; axial parenchyma paratracheal vasicentric; uniseriate and multiseriate (2-3 cells) rays; presence of phenolic compounds, mucilage and oil cells. Both species differ only in the location and frequency of oil/mucilage cells. The PCoA showed that wood anatomical characters effectively supported the diagnosis of tribes Cryptocaryeae, Laureae and Perseeae. The structure of the secondary xylem in Urbanodendronhave characters which are common to genera Aniba, Licaria, Nectandra, Ocotea and Persea, all belonging to tribe Perseeae, suggesting the placement of Urbanodendron in that same tribe. There were no quantitative statistically significant differences between cell elements present in individuals from both forest remnants.