Key anatomical attributes for occurrence of Psychotria schlechtendaliana (Müll.Arg.) Müll.Arg. (Rubiaceae) in different successional stages of a tropical moist forest

We analyzed the effects of two different successional stages on leaf and wood anatomy of Psychotria schlechtendaliana in a tropical moist forest. Leaf and wood samples were collected from plants growing in two sites representing two successional stages: advanced and intermediate stages of forest succession (ASFS and ISFS, respectively). The leaves have typical mesomorphic anatomy. Wood exhibits growth rings slightly different. The vessels elements are solitary, arranged radial or in clusters, with diffuse porosity, simple perforation plates, septate fibers, radial parenchyma multiseriate, and heterogeneous and perforated ray cells, intervessel pits bordered, small, alternate, vestured and/or scalariform. Quantitative analyses showed significantly differences in leaf and wood anatomy. Top and base leaves on both sites differed in the thickness of cuticle, palisade parenchyma, and palisade:spongy parenchyma ratio. Plants at ISFS had leaf lamina with thinner adaxial cuticle, smaller cells on the adaxial epidermis, smaller width of palisade parenchyma, smaller palisade:spongy parenchyma ratio, and lower stomatal density than at ASFS. The wood of plants in ISFS had presented smaller diameters of the lumen of vessels and fibers, higher frequencies of vessels and rays, and fiber and rays with longer lengths than at ASFS. The differences between leaf and wood anatomy at the two sites confirm a structural adjustment in relation to forest succession for this species. The anatomical differences reflect the sunlight distribution and water availability, allowing the adjustment in photosynthetic efficiency, and safety water transport.