Identity and localization of floral scent components in an androdioecious species, Chionanthus retusus (Oleaceae)

Abstract

Chionanthus retusus Lindl. & Paxton (Oleaceae) is an androdioecious species, in which male individuals coexist with hermaphroditic individuals. Even though the floral scent dimorphism of dioecious taxa has been reported elsewhere, little is known about the floral scent compounds of androdioecious species. The aim of the present study was to elucidate the identity and localization of floral scent components in C. retusus in both male and hermaphrodite. The headspace of whole flowers exhibited quantitative and qualitative floral scent dimorphism. Among several constituents, including phenylethyl alcohol, benzeneacetonitrile, 2-hexen-1-ol were the main fragrance component of both sexual morphotypes. In particular, the abundance of phenylethyl alcohol (2-phenylethanol), which is one of the compounds in pollen and pollenkitt, in both sexual morphotypes might provide indirect evidence for the viability and functionality of pollen grains. However, 3-hexen-1-ol, 1-hexanol, 3-hexenyl 2-metylbutanoate, alloaromadendrene, and farnesol were only detected in hermaphrodites. These patterns of floral scent difference suggest that several compounds solely detected in each sexual type are associated with specific reproductive organs. Comparative micromorphological and ultrastructural studies of floral surfaces (e.g. floral stomata, calyx glands) and pollen grains (especially pollenkitt) revealed that all represent a putative secretory structures and materials.

Keywords

• Chionanthus retusus
• Floral stomata
• Phenylethyl alcohol
• Pollenkitt
• SEM