Extrafloral nectary ontogeny of Triumfetta semitriloba (Tiliaceae)

摘要

Triumfetta semitriloba is a weed displaying floral and extrafloral nectaries, the latter being visited by ants that protect the plants. The objective of this work was to describe the ontogeny of the extrafloral nectaries of T. semitriloba, using nectary samples obtained from adult plants, in four developmental stages. The material was submitted to the usual techniques to obtain permanent slides. The nectaries initiate their development precociously, with the appearance of one concavity turned to the adaxial side, followed by clavated nectariferous trichomes, originated from protodermic cells, underlied by a nectariferous parenchyma vascularized by phloem and xylem, which are common features among the Malvales. The nectariferous trichome head cells present vacuoles with phenolic compounds, which may play an ecological role. Plastids are absent in the trichomes and are not conspicuous in the nectariferous parenchyma, possibly indicating their secondary importance in nectar secretion. The senescent nectary has relatively less nectariferous trichomes, which are invaded by hyphae covering the concavity at this stage. For a better understanding of the processes of nectar secretion and elimination, further transmission electronic microscope studies are needed.