Evolution of flowers and inflorescences in Euphorbiaceae
With about 6500 species, Euphorbiaceae represent one of the largest plant families. They include many species of considerable economic importance, such as cassava (Manihot esculenta), the rubber tree (Hevea brasiliensis) and the Barbados nut (Jatropha curcas). Euphorbiaceae show a broad morphological range of flowers, inflorescences and flower-like inflorescences, which are termed pseudanthia (or cyathia, in the specific case of Euphorbia).
Our main focus in this project is to evaluate character homologies across the family and to study the evolution of flower-like inflorescences such as the Euphorbia cyathium, which resembles a bisexual flower. Techniques applied include immunohistochemical localisation of proteins, scanning electron microscopy (SEM) and light microscopy (LM). For example, in a PhD project that was partly supervised at Kew, we analysed the floral morphology and development of selected Brazilian species of the giant genus Croton and related genera.
Based on detailed comparative morphological analysis placed in a phylogenetic context, evolutionary-developmental (Evo-Devo) work on the cyathium will reveal the genetic background for the formation of this highly derived structure. Our studies contribute to a better understanding of relationships among Euphorbiaceae genera. Detailed data on comparative floral and inflorescence morphology are the foundation for understanding these reproductive structures in an ecological context, including the pollinating agents and reproductive system.
Prenner G., Cacho N.I., Baum D.A., Rudall P.J. 2011. Is LEAFY a useful marker gene for the flower-inflorescence boundary in the Euphorbia cyathium? Journal of Experimental Botany 62: 345–350.
Cavalari da Silva O., Sajo M.G., Prenner G., Cordeiro I, Rudall P.J. 2011. Morphology development and homologies of the perianth and floral nectaries in Croton and Astraea (Euphorbiaceae-Malpighiales). Plant Systematics and Evolution 292: 1–14.
Prenner G., Vergara-Silva F., Rudall P.J. 2009. The key role of morphology in modelling inflorescence architecture. Trends in Plant Science 14: 302–309.
Prenner G., Hopper S.D., Rudall P.J. 2008. Pseudanthium formation in Calycopeplus paucifolius with particular reference to the evolution of the cyathium in Euphorbieae (Euphorbiaceae – Malpighiales). Australian Systematic Botany 21: 153–161.
Prenner G., Box M.S., Cunniff J., Rudall P.J. 2008. The branching stamens of Ricinus and the homologies of the angiosperm stamen fascicle. International Journal of Plant Sciences 169: 735–744.
Prenner G., Rudall P.J. 2007. Comparative ontogeny of the cyathium in Euphorbia (Euphorbiaceae) and its allies: exploring the organ-flower-inflorescence boundary. American Journal of Botany 94: 1612–1629.
Project partners and collaborators
David Baum, Ivalu Cacho; Dept. Botany, University of Wisconsin, Madison
Graca Sajo, Orlando Cavalari de Paula; Universidade Estadual Paulista (UNESP), Sao Paulo, Brazil.
John Pannell, John Russell; Dept. of Plant Sciences, University of Oxford.