Wood anatomy of Jacaranda (Bignoniaceae): Systematic relationships in sections Monolobos and Dilobos as suggested by twig and stem wood rays by

Abstract

This report provides a generic description of the stem wood anatomy of 15 species of Jacaranda from sections Monolobos and Dilobos. In Monolobos (excluding J. copaia), the rays are homocellular and exclusively uniseriate, occasionally with a small biseriate portion. In Dilobos, the rays are heterocellular and 2-3(-4) cells wide. To verify the differences in ray structure, 27 species of twig specimens were examined and compared with stem specimens of the same section. The wood anatomy corroborates morphological evidence that suggests partitioning of Jacaranda into two distinct sections and supports the hypothesis that section Dilobos is primitive. The wood anatomy of Jacaranda copaia is distinct from that of other species in the genus. The vessels are larger in diameter and fewer per square millimetre, the vessel elements and fibres are longer, and the number of cells per parenchyma strand is higher. In addition, the rays are fewer per millimetre, taller, and homocellular to slightly heterocellular, with one irregular row of square cells, 2-3(-4) cells wide. Jacaranda copaia seems to be intermediate between sections Monolobos and Dilobos.