A developmental approach expanding the knowledge of inflorescence diversity in subtribe Eleusininae (Chloridoideae: Poaceae)

Abstract

Abstract Subtribe Eleusininae (Chloridoideae, Poaceae) comprise 237 species with little morphological diversity in inflorescence structure. This diversity may be explained by an evolution from complex (pyramidal, highly branched) to simpler (digitate, barely branched) morphologies. However, only mature specimens have been studied; the developmental analyses of the inflorescences are rare. We analysed the inflorescence, spikelet and flower development of 17 species of Eleusininae using scanning electron microscopy. In the early stages of the transition to flowering of the studied species, the inflorescence meristem elongates initiating primary branches acropetally. The differentiation of these branches along the main axis is either basipetal or amphipetal. Although the initiation of secondary branches along primary branches may be acropetal or amphipetal, their differentiation follows an amphipetal direction. The florets in spikelets are initiated acropetally. We found abnormal orientation of stamens and gynoecium in florets of Leptochloa chloridiformis. The analysis of the ontogeny has enriched current knowledge of inflorescences in the subtribe. In addition, the developmental patterns revealed the existence of more than one developmental pattern leading to similar mature inflorescence forms. The results will support future efforts on postulating trends of developmental patterns across Poaceae.