Surface microsculpture and their contribution to distinguish seeds of Eichhornia azurea and E. crassipes (Pontederiaceae) of the Pantanal

Abstract

Eichhornia azurea and E. crassipes are morphologically easy to distinguish, however, their seeds are similar and differentiated only by size, which makes their identification difficult, especially when collected directly from the seedbank. We identified characters for distinguish seeds of these species through macrosculpture analyzes of the seed coat (size, shape, epidermal pattern, the structure of the primary and secondary microsculpture, funiculum, hilum, micropyle, raphe), using scanning electron microscopy. The species differ mainly by the secondary sculpture pattern, with perforated in E. azurea and wrinkled with micropapillae in E. crassipes; the external tissue of seed with smooth aspect in E. azurea and irregularly wrinkled in E. crassipes; and raphide crystals in E. crassipes. Our results contribute to taxonomy of the tribe Eichhornieae and future studies on the microsculpture analyzes of the macrophytes seed coat, in a comparative approach to understand ecological and evolutionary aspects.