ABSTRACT The Brazilian Pantanal is an extensive wetland with heterogeneous habitats, primarily due to the river-floodplain system and plants with differential adaptations and reproductive strategies. Factors such as altitude, distance among plant formations, and flood pulse must be considered to better understand its diversity. Aiming to assess the influence of biogeographic patterns in this system, we analyzed the floristic composition of six areas along the Paraguay River, including residual relieves, verifying the pattern of similarity, and effects of distance and altitude. We recorded 356 species in 87 families, mostly perennial (75%), and some annuals (15%) and pluriannuals (5%). Herbaceous plants were the most represented (48%), followed by arboreal (23%), shrubby (15%) and epiphytic (14%) habits, only 12% being endemic to Brazil. The studied areas showed low floristic similarity, but higher resemblance of species between neighboring areas, and no relation with altitude. The upper Paraguay River is diverse, with high spatial variability of species, predominantly perennial. The river-floodplain connectivity may be a determinant factor in species richness and occurrence of endemic species.

A presença de sistemas subterrâneos espessados em Asteraceae tem sido amplamente relatada na literatura. Devido à grande complexidade dos sistemas subterrâneos, que podem ser de natureza radicular, caulinar ou mista, as análises morfoanatômicas são importantes para assegurar a utilização da terminologia correta. Este estudo teve por objetivo descrever a morfoanatomia e ontogenia, investigar a presença de metabólitos secundários e avaliar os efeitos da sazonalidade no sistema subterrâneo de Chrysolaena simplex (Less.) Dematt. As amostras foram estudadas usando os protocolos padrão de anatomia vegetal, eletrônica de varredura, histoquímica e fitoquímica. O sistema subterrâneo de C. simplex foi identificado como rizóforo, que se originou do nó cotiledonar. Em indivíduos adultos, com rizóforos completamente desenvolvidos, as raízes primárias degeneram e formam sistemas radiculares adventícios. As gemas, nas porções subterrâneas, promovem o crescimento do rizóforo e formaram caules aéreos quando expostas à luz. Gotas lipofílicas foram evidenciadas nas células parenquimáticas do córtex e medula, endoderme e gemas. Frutanos tipo inulina foram evidenciados no eixo caulinar e gemas do rizóforo. A ocorrência de gemas, metabólitos secundários, frutanos e lipídeos armazenados no rizóforo, podem ser apontados como caracteres adaptativos.

The occurrence of thickened underground systems in Asteraceae is widely reported in the literature. Given the great complexity of underground systems, which may originate from roots, stems, or both, morpho-anatomical analyses are essential to ensure the use of correct terminology. The goals of this study were to describe the morpho-anatomy and ontogeny, investigate the occurrence of secondary metabolites and evaluate the effects of seasonality on the underground system of Chrysolaena simplex (Less.) Dematt. Samples were studied using standard protocols of plant anatomy, scanning electron microscopy, histochemical and phytochemical. The underground system of C. simplex was categorised as a rhizophore which started from cotyledonary node. In adult individuals, with rhizophores completely developed, the primary roots degenerated and adventitious radicular systems are formed. The buds in the subterranean portions promote the rhizophore growing, and form aerial stems when exposed to light. Lipophilic droplets were evident in the parenchymatous cells of the cortex and pith, endodermis and buds. Inulin-type fructans were observed in the stem axis and buds of the rhizophore. The presence of buds, secondary metabolites and the storage of fructans and lipids in the rhizophore can be seen as adaptive traits.