Ultrastructure of Osmophores in Restrepia (Orchidaceae)

Osmophores of the myophilous genus Restrepia (Orchidaceae) were studied developmentally at the ultrastructural level. They are located at petal apices and on the adaxial surface of the dorsal sepal apex. Up to and through anthesis a dense, osmiophilic exudate is synthesized probably in endoplasmic reticulum or in plastids of papillose epidermal cells, and then appears to be transported through the plasmalemma by granulocrine elimination. As the exudate is amassed, the cuticle ruptures to form numerous pores that extend from the cell wall. Mitochondria and amyloplasts are especially abundant at anthesis. From anthesis to post‐anthesis, lipid droplets appear in the cytoplasm and vacuoles of epidermal cells, and frequency of cell organelles drops markedly with increasing vacuolation.