engleski

Hermaphroditic, unseasonal flowering in "green oak", growing in Northern Dalmatia, Croatia

Hermaphroditic flowering has been observed on a single tree, the "green oak", a supposed hybrid between Quercus cerris and Q. ilex. That tree was systematically defined as Quercus x viridis Trinajstić, but it is unlikely that a hybrid of two species where acorns mature in the second year (Q. cerris L.) and in the first year (Q. ilex L.) could be found. For that reason, new investigation of that tree was conducted. In late autumn, on 3 November 1998, during acorn collection from the crown, unseasonal flowering was discovered on two branches. Flowers appeared to be stiff like female inflorescences, more elongated and with more flowers than normal. At the first glance, the presence of numerous stamens in the inflorescence was evident. Under a hand lens, 4–6 stamens could be seen, surrounding a pistillate flower with well-developed stigmas. Inflorescences and individual flowers were photographed. Pollen from hermaphroditic flowers was photographed by a scanning microscope. In spring, on 26 April, abundant flowering of normal male and female flowers was observed, photographed and analyzed. No aberrant morphology similar to flowers discovered in November 1998 could be seen in the crown of the "green oak". Papers describing occurrence of hermaphroditic flowering in some American oaks, especially the Gambel oak (Q. gambelii Nutt.) are discussed. Unseasonal flowering in "green oak" and the appearance of hermaphroditic flowers could not be explained by unusual climatic changes in the area. It could be speculated only that hermaphroditic flowering represent a primitive ancestral condition in the Fagaceae, as suggested by some of the authors discussed in the paper.

Key words: Quercus L.; hermaphroditic flowering; unseasonal flowering

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