Floral anatomy and development of species of Phyllanthaceae, Picrodendraceae, Euphorbiaceae and Pandaceae

• Ano de defesa: 2017
• Autor(a) principal: Gama, Thália do Socorro Serra
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Alchornea; Desenvolvimento floral; Floral development; MET; MEV; Microdesmis; Nectaries; Nectários; Phyllanthus; Piranhea; SEM; TEM; Vascularização; Vascularization
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/41/41132/tde-26062017-114819/

Euphorbiaceae s.l. are distributed in the most varied types of vegetation and habitat, being one of the biggests, most complexs and diversified families in the angiosperms. Its classification was discussed during long time by many authors and with the phylogenetic analyses was proved its polyphyletic origin, bearing the dissolution in six distinct families: Phyllanthaceae, Picrodendraceae, Putranjivaceae, Pandaceae, Peraceae e Euphorbiaceae s.s. Considering the floral diversity of these families, fours species were selected to this study, aiming to sample the different groups: Phyllanthus urinaria (Phyllanthaceae), Piranhea trifoliate (Picrodendraceae), Alchornea sidifolia (Euphorbiaceae s.s.) and Microdesmis caseariifolia (Pandaceae). There are few detailed literature about the floral structure of the representants from the allied families of Euphorbiaceae s.l., which makes difficult the accurate usage of the floral characters in studies about systematics and evolution of these groups. Furthermore, information on the functional implications of these characteristics in the biology of the species are limited. In this context, the aim of this work was analyse the floral morphology, with an emphasis on the development patterns, vascularization and secretory structures. For this purpose, floral buds and flowers in different stages of development were fixed, dehydrated, embedded in Paraplast or historesin, sectioned and stained, besides the SEM and TEM analysis that helped on the investigation of the floral ontogenesis and the nectariferous tissue. As main results of the structural analysis, we found that Phyllanthus urinaria has sepals and petals, as well Piranhea trifoliate, both from the clade Phyllanthaceae + Picrodendraceae. Then, flowers from these groups should be studied from its origin and vascularization to have a better understanding of the evolutionary path of the perianth in these families. Piranhea trifoliate also have staminodes that may indicate a transitional process during the evolution of the group. In Alchornea sidifolia we found development patterns that explain the formation of characteristics of anemophilous plant, such as the production of more flowers in the male inflorescences than the more compact and fewer flowered female inflorescences, the presence of unisexual flowers with reduced perianth, absence of nectaries, and female flowers with extensive stigmatic receptive surface. This species also has a peculiar characteristic regarding the number of carpels, which is generally three in the Euphorbiaceae and Malpighiales, even though A. sidifolia has two carpels. Microdesmis caseariifolia displayed variation in the number of stamens, shown a placental obturator and a pistilode, and all these features are novelties to the Pandaceae. This study adds to the floral knowledge of the different families, as well as enable to raise issues to be addressed in future studies about the structure and evolution of floral characters in Malpighiales