Estrutura foliar de Loudetiopsis chrysothrix (Nees) Conert e Tristachya leiostachya Nees (Poaceae)

Loudetiopsis chrysothrix e Tristachya leiostachya são espécies de gramíneas que apresentam grande similaridade morfológica, distinguindose pelo número de estames e pelas características da arista. Entretanto, tais estruturas são caducas e, freqüentemente, estão ausentes na espigueta madura o que dificulta a identificação. Visando reconhecer caracteres úteis na delimitação dessas espécies, neste trabalho foram estudadas a anatomia e a ultra-estrutura da lâmina foliar. Os caracteres diferenciais entre as duas espécies foram: disposição dos tricomas tipo espinho na superfície adaxial da lâmina; profundidade dos sulcos na superfície adaxial; formato das saliências nos feixes de primeira ordem; tamanho, posição e o arranjo dos feixes vasculares na lâmina foliar; contorno dos vasos de metaxilema; número de células da extensão da bainha dos feixes vasculares; presença/ausência de células incolores no mesofilo; número de estratos de células do clorênquima radiado e distribuição do esclerênquima subepidérmico. em ambas as espécies, os cloroplastos do clorênquima apresentam grana e ausência de grãos-de-amido; os da bainha são agranais, com ou sem grãos-de-amido. Outras características como a presença de ceras epicuticulares, estômatos alojados em sulcos na superfície adaxial, diferenças no grau de sinuosidade das paredes das células epidérmicas e na estrutura das paredes celulares são comuns a espécies de cerrados e podem estar relacionadas com a economia de água.Loudetiopsis chrysothrix and Tristachya leiostachya are grasses species showing great morphological similarity, but differing in stamen number and awn characteristics. However, these structures are deciduous and frequently absent in the mature espikelet, which makes their identification difficult. In order to recognize useful characters for species delimitation, this paper studied the leaf blade anatomy and ultrastructure. The different characteristics between these species were: prickle hair arrangement on the leaf blade adaxial surface; furrow depth on the adaxial surface; saliency shape on the first order bundle; vascular bundle size, position, and arrangement on the leaf blade; metaxylem vessel outline; number of cells in the bundle sheath extension; presence/absence of colourless cells in the mesophyll; number of chlorenchyma radiated cell strata and distribution of the sub epidermal scherenchyma. In both species, chloroplasts of the chlorenchyma show grana and absence of starch grains; those in the sheath are agranal, with or without starch grains. Other characteristics such as presence of epicuticular waxes, stomata in furrows on the adaxial surface, differences in the sinuosity degree of the epidermal cell wall, and cell wall structure are common in cerrado species and can be related to water saving.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Development and evolution of the gynoecium in Myrteae (Myrtaceae)

Characters of the gynoecium are considered potentially significant for the systematics of Myrtaceae. However, only two such characters - ovule number and placentation - have been addressed from an evolutionary perspective. Colleter presence in flowers is a synapomorphy of Myrtales; however, no morphological and histochemical descriptions of such structures have been done in Myrtaceae. Here we analysed the ontogeny and anatomy of the gynoecium combined with the ontogeny, anatomy, ultrastructure, and histochemistry of the colleters to study the evolution of these characters and map their states in the Myrteae phylogenetic tree. Our findings may help elucidate the evolutionary history of this tribe of fleshy-fruit producers so important towards maintaining ecological balance in the rainforest. Floral anatomy and ontogeny were analysed using light microscopy. Colleter samples were processed using standard methods for light and transmission electron microscopy. The main metabolites in colleters were detected via histochemistry. To map character states the program Mesquite version 2.71 was used. The morphological characters of the South American Myrteae here analysed provided an overview of the evolution of gynoecium - with cauline or carpellate placenta - and of colleters, as well as synapomorphies for the clades Plinia + Myrcia and Eugenia + Pimenta. The presence of two integuments in the ovules associated with sclereids and colleters in the gynoecium and the young fleshy fruit assures the efficient dispersal of their seeds. Our findings regarding gynoecium structural diversity of the tribe Myrteae give a new insight on their morphologically uniform flowers.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES