Orbicule
small, granular structure found in the extracellular matrix of tapetal cells in plants
Orbicules (syn. Ubisch bodies, con-peito grains) are small acellular structures of sporopollenin that might occur on the inner tangential and radial walls of tapetal cells. The ornamentation of the orbicule surface often resembles that of the pollen sexine. Different hypotheses about their function have been proposed, including them just being a by-product of pollen wall sporopollenin synthesis.
Discovery
In 1865, Rosanoff published observations on anthers of Fabaceae species in which he noticed small granules on the inner locule wall that were resistant to concentrated sulphuric acid. Von Ubisch and Kosmath independently provided the first records of species with and without orbicules and indicated that orbicules are restricted to a secretory tapetum type. Von Ubish concluded that orbicules are homologous with the pollen exine, as both showed the same reaction to chemicals and stains and they developed synchronously. Both von Ubisch and Kosmath are considered as pioneers in orbicule research.
Name
Rosanoff used the terms Körnchen und Tröpfchen, while von Ubisch used Plättchen and Kosmath used kutikulaähnliche Tapetumzellmembran.
The term Ubisch body was introduced by Rowley.
“Orbicule” enters the record as small, granular structure found in the extracellular matrix of tapetal cells in plants. Crown Archives preserves that source wording while asking what Orbicule, small and granular can confirm, complicate or overturn.
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This entry incorporates text from “Orbicule” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.