The Role of Floral Morphology and Epidermal Outgrowths in Etlingera elatior (Jack) R. M. Smith (Zingiberaceae) True Flower

Abstract

The inflorescence of Etlingera elatior forms tubular, true flowers in an acropetal sequence that blooms ostentatiously. The aromatic plant also produces excellent flavour and fragrance afforded by the presence of secretory structures capable of accumulating, storing, and releasing volatile compounds. However, there is a lack of botanical description of the flowering morphology and the type of secretory structures involved in plant-pollinator interactions. This study aims to describe the floral morphology, characterise the diverse micromorphology of the epidermal outgrowths in the true flower, and analyse their histochemical contents by scanning electron and light microscopes. Labellum defines the anthesis stage of the true flower: unveiling by petals at anthesis and furling inwards that closes the top part of the flower at post-anthesis. In addition to the floral advertisement accessory function demonstrated by the labellum, the closure provides additional exaptation of post-pollination protection to the flower. Both glandular trichomes and osmophores are involved in biochemical functions that release heterogeneous substances (mucilage, terpenes, and phenolic compounds) to help secure anthesis. Non-glandular trichomes, on the other hand, are structurally involved in the floral development by providing physical and mechanical protection to the flower by acting as glue to maintain the closed structure of the flower, connecting floral accessories, and forming a formidable barrier surrounding the ovary, the most important reproductive organ of the flower. Findings from the present study demonstrate that the presence of secretory structures coordinated with the flower’s functional traits enhances the pollination mechanism. It is the maiden report for E. elatior on epidermal outgrowths and their participation in floral structure and development besides plant-pollinator interaction.