The ontogeny of pollinia and elastoviscin in the anther of Doritis pulcherrima (Orchidaceae)

Wolter, M., Seuffert, C. & Schill, R. 1988. The ontogeny of pollinia and elastoviscin in the anther of Doritis pulscherrima (Orchidaceae). - Nord. J. Bot. 8: 77–88. Copenhagen. ISSN 0107–055X.
The ontogeny of pollinia of Doritis pulcherrima shows some features not commonly found in other angiosperms. The cell wails of the mature pollinium are almost identical with those of the pollen mother cells, and a callose envelope is lacking during the formation of sporopollenin. This fact may be related to the absence of a clear substructure of the exine and its low resistance to acetolysis. An exine is found only at the outer tetrads of the pollinium. The pollen grains in the tetrads possess irregularly spaced cell walls. The ontogeny of elastoviscin (specialized pollenkitt) begins in the ground cytoplasm of some tapetal cells, where small droplets are surrounded by myelin-like structures. Before anthesis the droplets fuse, flow into the loculus, and attach the pollinia to the stipe, thus forming a pollinarium. In the region in front of the elastoviscin-producing cells, some cells with specialized helical wall thickenings develop.