Micromorfologia do antécio superior de Digitaria Haller (Poaceae: Paniceae)

Abstract

The genus Digitaria (Poaceae: Paniceae) includes about 271 species and has a cosmopolitan distribution. The identification of its species is very complex, but it is extremely relevant because many species of the genus are weeds of crops of great importance to the country. For the marketing of seeds of these crops, there is a limit of the amount of spikelets/fruits for the species of Digitaria that can be found in seed lots, which is established by the Brazilian Ministry of Agriculture, Livestock and Supply (MAPA). Several studies have highlighted the importance of scanning electron microscopy (SEM) for the identification and delimitation of morphologically similar species, including representatives of the tribe Paniceae. In this context, the present work aimed to analyze the micromorphology of the upper anthecium of Digitaria species with the use of SEM, in order to assist in the distinction of taxa. We investigated 129 species of Digitaria (48% of the species accepted for the genus), from all continents. Eight distinct patterns of ornamentation of the upper anthecium were observed, which demonstrates that the micromorphological characters of the upper anthecium are of great importance for the taxonomy of the genus, helping the differentiation of morphologically similar species in many cases. The species analyzed also presented bicellular trichomes, stomata, and prickles in the upper anthecium, which are new characteristics that can also be used in the differentiation of the species of Digitaria.