The common name "wild indigo" specifies Indigofera anil L., I. suffruticosa Mill. (legitimate name) and I. truxillensis Kunth (legitimate name) that are very similar due to their external morphology. This work analyzed diagnostic characteristics of seeds and seedlings of these species since such features are widely used in taxonomic approaches within Leguminosae. We studied surface features and morpho-anatomy of seeds and cotyledons with scanning electronic microscopy and light microscopy, and described seedling phases. Although seedlings are similar, seed characteristics (size, shape, surface ornamentation, shape of the hilum and embryo size) and cotyledon characteristics (shape, trichome ornamentation, organization of spongy parenchyma along central veins and metabolite distribution in the tissues) have diagnostic features for the species. I. anil differs from I. suffruticosa in its larger seeds and acuminate-margined cotyledons. I. truxillensis is recognized by its cylindrical seeds and kidney-shaped cotyledons with large oil drops. We assume that the characteristics examined, plus fruit morphology and foliar anatomy suggest that I. anil, I. suffruticosa and I. truxillensis should not be synonymized.
anatomy; cotyledon; histochemistry; Indigofera; seed; taxonomy
