Floral structure in the Asian palm Eugeissona tristis Griff. (Arecaceae: Calamoideae), and description of a new nectary type in the family

Abstract

The South-East Asian palm genus Eugeissona has an unusual flower structure, and it occupies a basal position in the early divergent palm subfamily Calamoideae. This article describes the floral structure of Eugeissonatristis, a palm that has been associated with an uncommon pollination syndrome in which non-flying mammals ingest large amounts of fermenting nectar produced by flowers. Our study focuses on the architecture of the nectaries responsible for this nectar production. The nectariferous tissues differentiate in four histological regions along the length of the gynoecium, and appear to be primarily associated with ventral slits of the carpels, corresponding to pollen tube transmitting tracts (PTTT). Nectariferous tissues also develop along the carpel septa—as is typical for the Monocotyledons—but to a much lesser extent. A comprehensive review of the nectariferous systems diversity in palms confirms that it represents an undescribed type of nectary unique to the family, and demonstrates a topographical shift when compared to the septal or labyrinthine types typical of other palms. The non-flying mammal pollination syndrome observed in Eugeissona tristis is described and compared with similar syndromes in other angiosperms.