Evolution of the cyathium in Euphorbieae

The present project is a cooperation of Gerhard Prenner (Institute of Plant Sciences, Graz) and Paula Rudall (Royal Botanical Garden Kew). In the course of the project the evolution of flowers and inflorescences of spurges (Euphorbia) and their allies will be analyzed and interpreted. One of the best known members of the spurge family (Euphorbiaceae) is the Poinsettia or `Christmas flower` (Euphorbia pulcherrima), from tropical America. It is a popular decorative plant for the Christmas season because of its conspicuous red bracts. Succulent members are cultivated as indoor ornamentals. All species of the group have a latex which is often noxious, and some of it are of great medical importance. Furthermore, all spurges show peculiar floral features. The flowers are highly reduced and are aggregated to a blossom-like inflorescence which is called cyathium, and which is found in no other plant group. The present project focuses on the morphology and evolution of flowers and cyathia. It should be clarified, from which basic form the cyathium is derived and how the different shapes of cyathia can be interpreted in a systematic context. Cyathial morphology and development will be analysed by means of different microscopical techniques, like scanning electron microscopy and light microscopy. In a molecular focal point we want to clarify the genetic background of the formation of cyathia as well as the formation of the strongly reduced flowers. In this context, new insights into the basic knowledge of the formation of flowers and inflorescences are expected. Finally, the combination of the gained morphological and molecular data will allow new insights into the systematics of this highly interesting plant group.