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

Abstract

Within Chloridoideae, subtribe Eleusininae comprises 237 species with little morphological diversity in its inflorescence structure. This diversity may be explained by an evolution from complex (pyramidal shaped and highly branched) to simpler (digitated and barely branched) morphologies. However, only mature specimens have been studied; the developmental analyses of the inflorescences are rare. We analyzed the inflorescence, spikelet, and flower development of 17 species belonging to subtribe 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. Though the initiation of secondary branches along primary branches may be acropetal or amphipetal, their differentiation follows an amphipetal direction. The florets within spikelets are initiated acropetally. We found abnormal orientation of stamens and gynoecium within florets of Leptochloa chloridiformis. The analysis of the ontogeny enriched the current knowledge of inflorescences of the subtribe. In addition, the developmental patterns revealed the existence of more than one developmental pattern that leads to similar mature inflorescence forms. The results serve for future efforts on postulating trends of developmental patterns along Poaceae.