DiscolobiumandRiedeliella(Fabaceae – Faboideae – Dalbergieae clade): leaflet anatomy, secretory structures and their systematic implications

Abstract

AbstractDiscolobium and Riedeliella, exclusively South American genera, have been shown in phylogenetic analyses to be the sister group to the Pterocarpus clade. The species of the two genera can be confused when reproductive structures are absent, resulting in taxonomic misunderstandings in botanical collections. This study aimed to investigate the anatomical characters of leaflets of representatives of Discolobium and Riedeliella in terms of their diagnostic value at the genus and species levels and to provide information about the type, location and histochemistry of their secretory structures, and their usefulness for the systematics of the genera. The taxa were analysed using light microscopy and scanning electron microscopy. Unistratified epidermis, epidermal cell contour and fibre bundles of the main vein are features shared by the two genera. The position of the stomata and of the tector trichomes and the shape of the epidermal cells and of the mucilaginous idioblasts are diagnostic anatomical features at the genus level. Epidermal mucilaginous idioblasts are confirmed for all species studied. Phenolic idioblasts are present in Riedeliella and Discolobium, and secretory trichomes are found only in Discolobium. The anatomical characters of the leaflets are useful for the taxonomy of all species studied. Furthermore, our dataset shows novelties for the systematics of Fabaceae.