Micromorphology and histochemistry of labellum of Orchidantha foetida Jenjitt. & K. Larsen (Lowiaceae)

Orchidantha foetida Jenjitt. & K. Larsen (Lowiaceae) is an endemic species distributed in the eastern region of Thailand. The rotten scent emitted from the flowers plays a critical role in pollinator attraction. Here we show the micromorphology and histochemistry of O. foetida which may be involved in pollinator attraction. Lip transverse section presented papillae on the adaxial epidermis with large intercellular spaces at the sub-adjacent layer. Using SEM, conical papillae and bullose epidermis with rugose cuticular striation were found on the adaxial lip surface with several minute droplets of putative secreted remnants. Histochemical results revealed the location of a scent-containing structure on the adaxial epidermal cells which may act as osmophores with scent releasing function. These results revealed the floral characters of O. foetida which may relate and help in pollinator attraction.