Anatomy and ultrastructure of floral osmophores of Catasetum fimbriatum (Orchidaceae)

S.D. REPOSI; M.M. GOTELLI; TORRETTA, JUAN PABLO

PROTOPLASMA

SPRINGER WIEN

Lugar: Viena; Año: 2021 vol. 258 p. 1091 - 1102

0033-183X

Catasetumfimbriatum is a dioecious species whose flowers fully adapted to aneuglossinophilicmode of pollination. Euglossini male bees collect the volatilefragranceswhich are produced in osmophores on the flowers. In order to understandthemechanism of scent secretion and floral interaction with the pollinator, wedescribethelocation, histochemistry, anatomy and ultrastructure of osmophores inpistillate andstaminateflowers of this species. Fresh flowers were submerged in neutral red solutionto locatethe position of the osmophores. Other histochemical test performed includethe NADIreaction to detect terpenoids, Sudan IV for lipids, and Lugol´s iodine solutionto detectstarch. Anatomical and ultrastructural traits were studied with bright fieldandtransmissionelectron microscopes, respectively. The location of osmophores differsbetweenpistillate and staminate flowers. In pistillate flowers, secretory tissues wereobserved onthe ribbed adaxial surface of the labellum, but not on its margins, whereasinstaminate flowers, they were found throughout the adaxial surface of thelabellumandespecially in the fimbriae. Anatomy and ultrastructure of the osmophores in thelabellum ofboth types of flowers were similar. They present characteristics ofmetabolicallyactive cells, such as abundant mitochondria, rough endoplasmicreticulum,vesicles, plastids with starch grains, and lipid globules. Granulocrinesecretionand cycles of cytoplasmic contraction and expansion appear to allow therelease ofproducts without involving the rupture of the cuticle. Individuals of Eufrieseaauricepsand Euglossa sp . were captured in staminate and pistillate flowers but, itseemslikely, that only the former pollinates this orchid species.