A survey of the presence and morphology of orbicules in European allergenic angiosperms. Background information for allergen research

Allergenic activity in the atmospheric aerosol of small particles in the si ze range of a few micrometres or less may play an important role in causing allergic reactions in the lower regions of the lungs, often seen in pollin osis. Orbicules (= Ubisch bodies) are small, mostly spherical granules of s poropollenin, which can occur on the radial and innermost tangential wall o f secretory tapetum cells. In instances where orbicules of allergenic speci es are dispersed into the atmosphere, they may act as effective vectors of allergens. We investigated the presence and morphology of orbicules in 15 a llergenic species using scanning electron microscopy. Orbicules were presen t in all species investigated of the families Betulaceae, Chenopodiaceae, F agaceae, Poaceae, Polygonaceae, and Urticaceae. In the species of the Aster aceae and Oleaceae studied, orbicules were lacking. Almost all orbicules ob served were spiny. Their mean diameters range from 0.342 to 1.130 mum. Orbi cules can be part of the fraction of small particles in the size range of a few micrometres or less, emitted from the anthers. Our results clearly ind icate that a thorough investigation of the sites of allergens across the wh ole anther is required to reveal whether or not these orbicules possess all ergens.