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.

O aspecto geleificado da polpa de mamão é constantemente confundido com amadurecimento prematuro. Este trabalho caracterizou esse distúrbio fisiológico na polpa de frutos de mamão através de medidas de liberação de eletrólitos, conteúdo de Pi, peroxidação lipídica, firmeza da polpa, condudo mineral (Ca, Mg e K - na polpa e semente) e análises histológicas da polpa. Os resultados mostram que o aspecto geleificado da polpa de mamão não está associado com o amadurecimento prematuro. Os resultados indicam uma redução da entrada de água no vacúolo como a principal causa da perda de turgor celular, enquanto o aspecto encharcado da polpa pode ser devido ao acúmulo de água no apoplasto.

Gelled aspect in papaya fruit is typically confused with premature ripening. This research reports the characterization of this physiological disorder in the pulp of papaya fruit by measuring electrolyte leakage, Pi content, lipid peroxidation, pulp firmness, mineral contents (Ca, Mg and K - in pulp and seed tissues), and histological analysis of pulp tissue. The results showed that the gelled aspect of the papaya fruit pulp is not associated with tissue premature ripening. Data indicate a reduction of the vacuole water intake as the principal cause of the loss of cellular turgor; while the waterlogged aspect of the tissue may be due to water accumulation in the apoplast.

Treze espécies de Crotalaria foram analisadas quanto aos compostos nitrogenados presentes na seiva do xilema. Os aminoácidos foram os principais compostos nitrogenados encontrados, e apenas traços de ureídeos estavam presentes. Uma análise da composição de aminoácidos realizada para quatro espécies revelou que a asparagina é o aminoácido predominante, representando mais de 68% do nitrogênio transportado. Nenhum desvio marcante deste padrão foi encontrado entre espécies, entre plantas noduladas e não-noduladas e nem entre estádios florais e vegetativos. Chegou-se a conclusão de que as espécies aqui estudadas possuem metabolismo de nitrogênio baseado na asparagina, concordando com dados da literatura para muitas outras espécies de leguminosas que pertencem à categoria de não-produtoras de ureídeos.

Thirteen species of Crotalaria were analysed for nitrogen compounds in the xylem root bleeding sap. Amino acids were the main form of organic nitrogen found, but only traces of ureides were present. Of the four species analysed for amino acid composition, asparagine was found to be the major amino acid, accounting for over 68% of the nitrogen transported. No striking deviations from this general pattern was found between species, between vegetative and floral stages of development, or between nodulated and non-nodulated plants. It was concluded that the Crotalaria species studied here have an asparagine-based nitrogen metabolism, consistent with many other non-ureide-producing legume species.