Euphorbiaceae is a wide family known by its floral morphology variation and by the presence of different cyme or racemose inflorescences. This flower and inflorescences variation is notable in Croton L., the second largest genus in the family, which is composed of about 1.200 species, with a notable diversity of floral shapes and different structures in pistillate and staminate flowers and also different architecture patterns of the inflorescence. Most of the flowers in Croton are distributed in thyrse inflorescences, in which the basal pistillate flowers are sometimes solitary and the staminate flowers are arranged in cymes and distally located, though some authors have described three thyrse patterns, which show staminate and pistillate flowers differently distributed along the inflorescence axis. These flowers and inflorescences variations may be better comprehended through morphological analysis, ontogeny, and the homeotic gene expression during the floral development, all comprising the evolutionary developmental area (evo-devo). The aim of this research is to investigate the flowers morphology and the inflorescence ramification patterns of Croton L., thus associate this with genetic inferences about the homeotic genes expression, in order to comprehend some steps that during the evolution originated different thyrses and different structures in Croton flowers, also helping on the comprehension of the evolution of flowers in Euphorbiaceae. The material to be analyzed in this study will be obtained from exsiccates comprising Croton L. species, which is deposited at the Royal Botanic Gardens Kew Herbarium. The species will be characterized morphologically using the respective specimen and the relevant characters will be documented using stereomicroscope. The expected results from the internship abroad are to support the hypothesis that there are transitory structures in the pistillate and staminate flowers of Croton, such as staminodes and nectaries, and also to state that probably there are more than three inflorescence patterns in Croton, thereby discussing that homeotic genes have different expressions in each type of inflorescence.Keywords: gene expression, flower morphology, pistillate flowers, staminate flowers, thyrse.
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