Floral resins of Philodendron adamantinum (Araceae): secretion, release and synchrony with pollinators

Philodendron is the only genus of Araceae in which resin release occurs in the inflorescence. The resinous secretion adheres to the smooth body surface of the pollinating scarab beetles and allows attachment of pollen grains, making its transport possible. In order to understand the process of resin synthesis and release to the external environment, we used structural, ultrastructural and histochemical analyses at different stages of development of the inflorescences of Philodendron adamantinum. Two types of secretory canals were observed in the spathe: small caliber canals near the abaxial face, and larger caliber canals in the adaxial region. Only the latter canals release secretion into the external environment. The secretory epithelium in these canals is formed by a layer of cuneiform cells, and exhibits secretory activity throughout the development of the spathe. Resin exudation is a peculiar characteristic of these canals and appears to result from pressure exerted by the secretory epithelium and by structural modifications in the wall of cells adjacent to the epidermis, which allow the formation of a separation zone whereby the resin is released. The observed synchrony between anther dehiscence and resin exudation of P. adamantinum enhances the role of this secretion in the pollination process.