Pollen dispersal units of selected Orchidoideae and their morphological, ultrastructural, and chemical features

This study focusses on the structural diversity of pollen dispersal units and pollen wall ultrastructures within Orchidoideae, the second largest of the five orchid subfamilies. Orchidoideae are monandrous, i.e. they have only one fertile anther producing predominantly sectile pollinia. Using a variety of methods, including combined light and electron microscopy and various staining and contrasting media, this research aims to expand playnological knowledge of orchidoid pollen. The study provides new insights into pollen morphology and ultrastructure of six Orchidoideae species and compares them with previously studied epidendroid species to identify shared and/or distinctive characteristics within these subfamilies. Our findings revealed not only deviations from the classic angiosperm pollen wall depending on the pollen package type but also differences in pollen wall structures both within the Orchidoideae and compared to the Epidendroideae. Detection reactions and contrasting methods provide further insights into the chemical composition of elastoviscin, essential for pollinia/pollinaria formation, and suggest, that the term elastoviscin encompasses a range of chemically distinct substances.