Resumo Informações sobre padrões fenológicos das plantas ajudam a entender a estrutura e o funcionamento dos ecossistemas e apóiam projetos de restauração em áreas degradadas. O objetivo deste estudo foi caracterizar a fenologia reprodutiva em indivíduos de Avicennia germinans e Laguncularia racemosa em uma floresta de mangue no estuário do rio Mamanguape, Nordeste do Brasil. O registro foi realizado mensalmente de Julho 2016 a Junho 2017. Aplicamos estatística circular para detectar tendências sazonais, calculamos a sincronia intra-específica e realizamos regressões entre fenofases e variáveis abióticas. Avicennia germinans exibiu respostas sazonais para botões florais, flores em antese e frutos, com um episódio reprodutivo por ano (padrão anual). Laguncularia racemosa não mostrou resposta sazonal, com um episódio por ano para botões florais (padrão anual) e dois episódios para flores em antese e frutos (padrão subanual). As fenofases reprodutivas de A. germinans apresentaram maior sincronia intra-específica do que L. racemosa. Fornecemos evidências de que a temperatura, a radiação solar e a precipitação são fatores importantes para o ritmo da floração em ambas as espécies. Em conclusão, os resultados deste estudo mostraram que as espécies exibiram diferentes respostas fenológicas, mesmo estando submetidas às mesmas condições abióticas.

Abstract Information on plant phenological patterns aids in understanding the structure and functioning of ecosystems and support restoration projects in degraded areas. The aim of this study was to characterize the reproductive phenology of Avicennia germinans and Laguncularia racemosa in a mangrove forest in the Mamanguape River estuary in northeastern Brazil. The characterization was performed monthly from July 2016 to June 2017. We applied circular statistics to detect seasonal trends, calculated intra-specific synchrony, and performed regressions between the reproductive phenophases and the abiotic variables. Avicennia germinans exhibits seasonal responses to floral buds, flowers at anthesis, and fruit, with one reproductive episode per year (annual pattern). Laguncularia racemosa has no seasonal response, with one reproductive episode per year for floral buds (annual pattern) and two episodes for flowers at anthesis and fruits (subannual pattern). Reproductive phenophases of A. germinans exhibited higher intra-specific synchrony than L. racemosa. We provide evidence that temperature, solar radiation and rainfall are important drivers of the flowering rhythm in both species. In conclusion, the results of this study showed that the species exhibited different phenological responses, even though they were subjected to the same abiotic conditions.

Gas exchange, chlorophyll afluorescence, and photosynthetic pigments of Xylopia sericeaA. St.-Hil. and Siparuna guianensis Aubl. were evaluated during the rainy season and the dry season (2009-2010) in three understories with different ecological conditions (irradiance, water availability, and temperature) located in the União Biological Reserve (known as REBIO União), at Rio de Janeiro State, a natural forest understory, eucalyptus understory under regeneration, and understory of eucalyptus plantation with 18-year-old trees that were removed 1 year before. The lowest values of Fv/Fm e Fm/Fo were observed in the exposed understory for both seasons, with lower values in the dry season, suggesting that reduced water availability potentializes the photoinhibitory process. For both species of the exposed understory it is suggested the occurrence of photoprotection, given that an increased proportion of carotenoid pigments in relation to the chlorophylls were verified. Both species still exhibited dynamic photoinhibition after 1 year of exposure to full sunlight (exposed understory) in both seasons, but more markedly so in the dry season, though they belong to early stages of ecological succession. Based on the results, it is suggested that these species are indicated for planting in degraded areas and that the cutting of eucalyptus trees as management practice should be performed in a gradual manner, during the rainy season, in order to minimize stress on these species.

In this work, the structural and ecophysiological alterations (chlorophyll a fluorescence and photosynthetic pigments), and quantification of Cr, Pb and Zn in the leaf limb, petiole and younger and older roots of water hyacinth from the lower, medium and upper Paraíba do Sul river (PSR) and Imbé river were evaluated. The plants from the medium and upper PSR (more industrialized and populated regions) exhibited lower turgid cell in the root cortex, less root hairs and leaf epidermis, chloroplasts with plastoglobules and increased stroma volume. Higher concentrations of metals were observed in the younger and older roots from the medium PSR plants. The results suggested that the plants from more anthropized regions were able to maintain the maximum quantum yield (Fv/Fm) which was a result from the metabolic fitting, increasing the non-photochemical quenching, reducing total chlorophyll/carotenoids and leading to the structural modifications.

As adaptações ecofisiológicas de aguapé (hiperacumuladora de metais) sob condições ambientais adversas ainda não estão totalmente elucidadas. Este trabalho avaliou pigmentos fotossintéticos e fluorescência da clorofila a em aguapé coletados em diferentes regiões (alto, médio e baixo) do rio Paraíba do Sul (RPS) e no rio Imbé, Brasil. Adicionalmente Mn, Fe, Zn, Cu, Pb e Ni foram quantificados na parte área e raízes. Ferro e Mn foram os elementos detectados em maiores concentrações em todas as amostras. Zinco e Cu foram detectados em maiores concentrações nas raízes de plantas do médio e alto RPS, locais de grande atividade antropogênica. As mais elevadas concentrações de quase todos os metais foram verificadas nas plantas do médio RPS. Com relação às adaptações fotossintéticas, plantas do médio e alto RPS mostraram as maiores concentrações de pigmentos fotossintéticos, assim como os mais elevados valores de Fv/Fm e Fv/F0. As avaliações fotossintéticas destas plantas sugerem que elas não estejam sob condições de estresse, mesmo nas regiões de grande atividade antropogênica. Correlação positiva foi observada entre quenching não-fotoquímico e carotenóides, sugerindo que a dissipação de energia na forma de calor seja uma estratégia para manter o funcionamento fotossintético fotoquímico estável, confirmado pelos valores de Fv/Fm. É possível que esta estratégia adaptativa seja eficiente como resposta de longo prazo, uma vez que na literatura esta não parece ser a via preferencial de adaptação a estresses de curto prazo, avaliados sob condições controladas.

The ecophysiological adaptations of water hyacinth (metal hyperaccumulator) under adverse environmental conditions are not yet clearly elucidated. This work evaluated photosynthetic pigments and chlorophyll a fluorescence in water hyacinth plants sampled in different regions (upper, middle and lower) of Paraíba do Sul river (PSR) and Imbé river, Brazil. Additionally Mn, Fe, Zn, Cu, Cr, Pb and Ni were quantified on the shoots and roots. Roots were the preferential site of metal accumulation. Cromium was not detected in the shoots. Iron and Mn were the elements detected in higher concentrations in all samples. Zinc and Cu were detected in higher concentrations in roots of plants from middle and upper PSR, sites of higher anthropogenic activity. The highest concentrations of almost all metals were verified in plants from middle PSR. Regarding photosynthetic adaptations, plants from middle and upper PSR showed the highest concentrations of photosynthetic pigments, as well as the highest values of Fv/Fm and Fv/F0. The photosynthetic performance of plants suggests that they are not under stress conditions, even in regions of higher anthropogenic activity. Positive correlation was observed among nonphotochemical quenching and carotenoids, suggesting dissipation of energy in the form of heat as an strategy to keep the stable photochemical photosynthesis functioning, confirmed by values of the Fv/Fm. It is possible that such adaptative strategy is efficient as a long term response to stress factors, once literature data suggest that this is not a preferential path for photosynthesis in stress circumstances under short time controlled conditions.