Orbicule
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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.
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. This name was however later rejected by Heslop-Harrison because they were not discovered by von Ubisch. In early Japanese literature, they are sometimes called con-peito grains. However, the most commonly used name is orbicule, which was coined by Erdtman and colleagues. ==Morphology== Orbicules are morphologically variable. Their size ranges from
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