Wood Anatomy of Placothira (Loasaceae)

Abstract

Wood anatomy of the single species of Plakothira, a recently discovered genus from the Marquesas Islands, is described qualitatively and quantitatively. Features new for the family include presence of vasicentric scanty axial parenchyma and presence of perforated ray cells. Plakothira has several wood features specialized for Loasaceae: vasicentric axial parenchyma, extremely reduced borders on fibertracheids, and storying in fiber-tracheids. Wood of Plakothira is clearly loasaceous. Storying in fibertracheids is reported here for the loasaceous genera Fuertesia and Mentzelia. Wood anatomy of Plakothira represents paedomorphosis in great length of vessel elements, erectness of ray cells, lack of change in large primary rays, and in presence of occasional scalariform perforation plates. Plakothira has wood features maximally mesomorphic for the family, correlating with its cloud-forest habitat and semisucculent wood and cortex structure.