Structure of monomerous diaspores of Pandanus (Pandanaceae): further steps for interpretation of their nature

Abstract

In order to reveal the structure of the monomerous diaspores of Pandanus, to clarify the position of the ovary and to determine its morphogenetic fruit type the fruits of P. austrosinensis and P. conglomeratus were studied. The fruiting carpel is differentiated into the proximal part (zone of the locule) and the distal part (pileus). In the proximal part, the exocarp is single-layered or lacking in case of carpel fusion, the mesocarp includes numerous scattered vascular bundles comprising 3 circles and is differentiated into peripheral (parenchymatous) and inner (sclerenchymatous) zones. The inner mesocarp and the single-layered sclerenchymatous endocarp comprise a stout stone. Since the structural type of the gynoecium and the nature of the female fructifications of Pandanus are currently undetermined their diaspores the studied species could be treated as monomerous drupes of Prunus type or as a fruiting carpel of polymerous pyrenarium of Butia type.