Angela Pierre Vitória

Antioxidant enzymes responses to cadmium in radish tissues

To investigate the antioxidant responses of radish (Raphanus sativus L.) to cadmium (Cd) treatment, seedlings of a tolerant variety were grown in increasing concentrations of CdCl(2), ranging from 0.25-1 mM, for up to 72 h in a hydroponic system. Analysis of Cd uptake indicated that most of the Cd accumulated in the roots, but some was also translocated and accumulated in the leaves, especially at the higher concentrations of Cd used in the experiments. Roots and leaves were analysed for catalase, glutathione reductase and superoxide dismutase activities. Catalase and glutathione reductase activities increased considerably in the roots and leaves after 24 h exposure to the metal, indicating a direct correlation with Cd accumulation. The analysis of native PAGE enzyme activity staining, revealed several superoxide dismutase isoenzymes in leaves, with the two predominant isoenzymes exhibiting increases in activity in response to Cd treatment. The results suggest that in radish, the activity of antioxidant enzymes responds to Cd treatment. The main response may be via the activation of the ascorbate-glutathione cycle for the removal of hydrogen peroxide, or to ensure the availability of glutathione for the synthesis of Cd-binding proteins.

Effects of Cadmium on Antioxidant Enzyme Activities in Sugar Cane

Sugar cane (Saccharum officinarum L. cv. Copersucar SP80-3280) seedlings were grown in nutrient solution with varying concentrations (0, 2 and 5 mM) of cadmium chloride for 96 h. Leaves were analysed for catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD) activities. Although a clear effect of CdCl2 on plant growth was observed, the activity of SOD was not altered significantly. However, the CAT activity decreased as the concentration of CdCl2 increased. GR exhibits a significant increase in activity at 2 and 5 mM CdCl2. CAT and SOD isoenzymes were further characterised by analysis in non-denaturing PAGE. Activity staining for SOD revealed up to seven isoenzymes in untreated control and 2 mM CdCl2 treated plants, corresponding to Cu/Zn-SOD isoenzymes. At 5 mM CdCl2, only six Cu/Zn-SOD isoenzymes were observed. No Fe-SOD and Mn-SOD isoenzymes were detected. For CAT, one band of activity was observed.

CHANGES IN ANTIOXIDANT ENZYME ACTIVITIES IN SOYBEAN UNDER CADMIUM STRESS

Soybean (Glycine max L.) seedlings were grown in a hydroponic system containing nutrient solution with varying concentrations (0, 0.01, 0.5 mM) of cadmium (Cd) for a 48 h period. Roots and leaves were analyzed for catalase, glutathione reductase, and superoxide dismutase activities. Although a clear effect of Cd on plant growth was observed, the activities of catalase and superoxide dismutase were not altered significantly in the roots or leaves at all concentrations tested. Glutathione reductase did not exhibit any variation in activity in leaves, however, in roots an increase in activity was observed at 0.5 mM Cd. Catalase and superoxide dismutase isoenzymes were further characterized by analysis in non-denaturing PAGE. Activity staining for superoxide dismutase (SOD) revealed seven isoenzymes in leaves and eight isoenzymes in roots, corresponding to Mn-SOD and Cu/Zn-SOD. No Fe-SOD isoenzymes were observed. For catalase, one band of activity was observed in leaves and roots. Although no significant variation was observed in leaf tissue, in roots the 0.5 mM Cd treatment exhibited a slight increase in catalase activity. The results suggest that in soybean, glutathione reductase is stimulated by Cd in roots, to produce reduced glutathione to be used in the synthesis of phytochelatins or possibly as a response to the generation of reactive oxygen species induced by Cd.

Structural changes in radish seedlings exposed to cadmium

Radish (Raphanus sativus L. cv. Redondo Vermelho) seedlings were analysed by light and scanning electron microscopy to characterize the structural changes caused by the exposure to 0.5 or 1.0 mM cadmium chloride for 24, 48 and 72 h. The analyses showed changes in the anatomical and morphological characteristics of roots, stems and leaves of two-week-old seedlings. In all tissues, pressure potential was decreased. Premature death with the disintegration of the epidermis and an increase in the number of root hairs was observed in roots exposed to Cd. The stem of seedlings exposed to Cd exhibited more cells layers in the cambial region. The main effects observed in leaves in response to Cd were stomatal closure, lack of cell wall thickening and alterations in the shape of the chloroplasts. It is suggested that the structural changes observed in seedlings treated with Cd were mainly caused by a Cd-induced decrease in water uptake.

Photosynthetic performance and anatomical adaptations in Byrsonima sericea DC. under contrasting light conditions in a remnant of the Atlantic forest

A dinâmica fotossintetica da especie pioneira tropical Byrsonima sericea DC. foi estudada durante o processo de regeneracao de uma mata nativa por avaliacoes ecofisiologicas (trocas gasosas, fluorescencia da clorofila a e conteudo de pigmentos fotossinteticos) e parâmetros anatomicos das plantas em ambientes ensolarados e sombreados. As avaliacoes ecofisiologicas foram feitas mensalmente por um ano e os dados foram agrupados em estacao seca e chuvosa. Byrsonima sericea DC. apresentou plasticidade anatomica que a capacita a se estabelecer em ambientes com contrastantes condicoes luminosas. Nas condicoes ensolaradas, ela produz lâmina foliar mais espessa (cerca de 420 µm) e epiderme adaxial plana, enquanto em ambientes sombreados, as folhas apresentaram a epiderme convexa e lâmina mais delgada (cerca de 393 µm). Nao foram encontradas diferencas significativas na composicao de pigmentos em funcao do ambiente, no entanto, durante a estacao seca, as plantas apresentaram concentracoes significativamente maiores de pigmentos fotossinteticos. As plantas de ambientes ensolarados mostraram diminuicao na razao Fv/ FO (na estacao chuvosa) e NPQ (na estacao seca), mas nao foram observadas diferencas entre as plantas de sol ou sombra numa mesma estacao do ano. Taxas fotossinteticas significativamente maiores foram encontradas na estacao chuvosa para as plantas de sol quando comparadas com as plantas de sombra (9.9±0.8 e 7.4±0.3 µmol m-2s-1, respectivamente). Aumento significativo na transpiracao foi observado em plantas de sombra durante a estacao seca, mas sem afetar a eficiencia no uso da agua. Dados ecofisiologicos sugerem que, principalmente as plantas mais expostas ao sol sofreram limitacoes hidricas durante a estacao seca e que, na estacao chuvosa, estas plantas aumentaram sua taxa fotossintetica. Isso possivelmente foi devido a maior forca de dreno resultante do maior crescimento neste periodo. Os dados sugerem que alteracoes anatomicas, especialmente a epiderme adaxial convexa, estariam auxiliando na captacao de luz nas plantas sombreadas durante ambas as estacoes, prevenindo alteracoes nos pigmentos, como o aumento de clorofila b geralmente observado em plantas de sombra, mas nao detectado no presente estudo. Outra consequencia da maior quantidade de luz capturada por estas plantas de sombra foi que, durante a estacao seca sua taxa fotossintetica nao diferiu da das planas de ambientes ensolarados. No entanto, quando a agua nao foi um fator limitante, um melhor desempenho fotossintetico foi observado nesta especie pioneira, em ambientes abertos.

RESPONSE OF RICE INBRED LINES TO CADMIUM EXPOSURE

ABSTRACT The response of a group of rice (Oryza sativa L.) genotypes to cadmium (Cd) exposure was tested using root growth as a parameter over the duration of the treatment. Three distinct response patterns were identified: a significant initial (0.01 mM) dosage effect, which was maintained with the increase of CdCl2 concentration to 1 mM; a significant initial effect, which was intensified with the increase of CdCl2 concentration, resistant to the CdCl2 concentration tested shown by a group of varieties. Significant interactions between dosage and varieties were observed. Enzymatic assays for catalase and glutathione reductase were also carried out in plants exposed to CdCl2. Similar response patterns for both enzymes were observed. The activities of catalase and glutathione reductase in leaves and roots were increased, and in the case of glutathione reductase in roots, such an increase was highly significant, suggesting that the synthesis of reduced glutathione may be stimulated for subsequent synthesis of phytochelatins or to dismutate the reactive oxygen species produced by the induced Cd stress.

Photosynthetic analyses of two native Atlantic Forest species in regenerative understory of eucalyptus plantation

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 Uniao Biological Reserve (known as REBIO Uniao), 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/Fme Fm/Fowere 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.

Ecophysiological adaptation and metal accumulation in water hyacinth from two tropical rivers

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 Paraiba do Sul river (PSR) and Imbe 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.

Photoacclimation capacity in seedling and sapling of Siparuna guianensis (Siparunaeae): Response to irradiance gradient in tropical forest

Light is a limiting factor in plant establishment and growth in the understory of forests. In this paper, we assessed acclimation capacity of Siparuna guianensis, an early secondary successional species. We used seedlings and saplings in three regeneration areas with different irradiance regimes to determine the traits that confer photoplasticity. We examined whether these traits differ at different developmental stages. Anatomical characteristics, photochemical efficiency, photosynthetic capacity, and growth were analyzed. Multivariate component analysis revealed the formation of six clusters: three for seedlings (one for each regeneration area) and three for saplings (following the same pattern of seedlings, considering the area). Increased irradiance favored photosynthetic performance, independently of the developmental stage. The same trend was observed for most data on chlorophyll (Chl) a fluorescence and the ratios of net photosynthetic rate/intercellular CO2 concentration (PN/Ci) and PN/PPFD. No parameter indicated photoinhibition stress. The CO2− and light-response curve data indicated that seedlings were already acclimated to tolerate variation in irradiance. Anatomical adaptations, such as thickness of leaf blade and of adaxial cuticle, were observed in individuals growing in areas with higher irradiation. Thinning of spongy parenchyma and higher investment into a plant height were observed in seedlings, possibly due to the vertical stratification of CO2 and light in the understory; because light is a more limiting resource than CO2 in the lower stratum of the forest. Photoplasticity in S. guianensis is associated with a set of morphological, anatomical, photochemical, and biochemical traits, whereas biochemical performance is best acclimated to variation in irradiance. These traits differed in seedlings and saplings but they were modulated mainly by irradiance in both developmental stages.

Structural and ecophysiological alterations of the water hyacinth [Eichhornia crassipes (Mart.) Solms] due to anthropogenic stress in Brazilian rivers

In this work, the structural and ecophysiological a lterations (chlorophyll a fluorescence and photosyn thetic pigments), and quantification of Cr, Pb and Zn in t he leaf limb, petiole and younger and older roots o f water hyacinth from the lower, medium and upper Paraiba driver (PSR) and Imbe river were evaluated. Th e 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, chlorop lasts with plastoglobules and increased stroma volu me. Higher concentrations of metals were observed in the young er and older roots from the medium PSR plants. The results suggested that the plants from more anthropized reg ions were able to maintain the maximum quantum yiel d (Fv/Fm) which was a result from the metabolic fitting, incr easing the non-photochemical quenching, reducing to tal chlorophyll/carotenoids and leading to the structur al modifications.