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      Avaliações fisiológicas e bioquímicas de plantas de aguapé (Eichhornia crassipes) cultivadas com níveis excessivos de nutrientes Translated title: Physiological and biochemical evaluations of water hyacinth (Eichhornia crassipes), cultivated with excessive nutrient levels

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          Plantas de aguapé foram cultivadas em solução nutritiva de Hoagland & Arnon n.2, cujo aumento dos níveis de N, P e Cu estabeleceu as diferenças entre os tratamentos. Utilizou-se o delineamento experimental inteiramente casualizado, com quatro repetições. As variáveis fisiológicas avaliadas foram área foliar, peso de matéria seca e taxa de crescimento absoluto, taxa de crescimento relativo, taxa assimilatória líquida, razão de área foliar, peso específico de folha, área foliar específica. Foram determinados também os teores de açúcares totais e redutores e de aminoácidos totais e a atividade das enzimas glutationa S-transferase e superóxido dismutase. Os extratos enzimáticos foram obtidos da matéria fresca da parte aérea das plantas. Após a coleta, foram determinados os pesos de material seco de raízes, pecíolos e folhas, que foram utilizados para a determinação de açúcares solúveis totais e redutores e de aminoácidos. O excesso de nitrogênio causou aumento de açúcares nas folhas e de aminoácidos nas raízes. Já o tratamento com excesso de fósforo levou ao aumento de açúcares nas raízes. Os resultados apresentados sugerem que, entre os nutrientes em excesso avaliados, o cobre (0,12 mg L-1) foi o maior indutor da atividade da GST e SOD, sugerindo que este elemento induziu estresse nas plantas de aguapé.

          Translated abstract

          Water hyacinth plants were cultivated in a Hoagland & Arnon n.2 nutrient solution with increased N, P and Cu levels establishing the differences among the treatments. The experimental design was completely randomized, with four replicates. Physiological evaluations included leaf area, dry matter and growth analysis parameters (absolute growth rate, relative growth rate, net assimilatory rate, leaf area ratio, specific leaf weight, specific leaf area). Biochemistry evaluations were total and reducing sugars, total amino acids and activity of the antioxidant enzymes (glutathione S-transferase and superoxide dismutase). The enzyme extract was obtained from fresh matter of the aerial part of the plants. Root and leaf dry material was used to determine total and reducing sugars, and amino acids. Nitrogen supplementation caused increased levels of sugars in the leaves and of amino acids in the roots. The treatment with excess phosphorus caused increased levels of sugars in the roots. The results suggest that copper (0.12 mg L-1) increased the activity of GST and SOD, inducing stress in the water hyacinth plants.

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          Most cited references 30

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          Strategies of antioxidant defense.

           H Sies (1993)
          Cellular protection against the deleterious effects of reactive oxidants generated in aerobic metabolism, called oxidative stress, is organized at multiple levels. Defense strategies include three levels of protection; prevention, interception, and repair. Regulation of the antioxidant capacity includes the maintenance of adequate levels of antioxidant and the localization of antioxidant compounds and enzymes. Short-term and long-term adaptation and cell specialisation in these functions are new areas of interest. Control over the activity of prooxidant enzymes, such as NADPH oxidase and NO synthases, is crucial. Synthetic antioxidants mimic biological strategies.
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            Glutathione S-transferases (GSTs) play roles in both normal cellular metabolism as well as in the detoxification of a wide variety of xenobiotic compounds, and they have been intensively studied with regard to herbicide detoxification in plants. A newly discovered plant GST subclass has been implicated in numerous stress responses, including those arising from pathogen attack, oxidative stress, and heavy-metal toxicity. In addition, plant GSTs play a role in the cellular response to auxins and during the normal metabolism of plant secondary products like anthocyanins and cinnamic acid. This review presents the current knowledge about the functions of GSTs in regard to both herbicides and endogenous substrates. The catalytic mechanism of GST activity as well as the fate of glutathione S-conjugates are reviewed. Finally, a summary of what is known about the gene structure and regulation of plant GSTs is presented.
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              Superoxide dismutases: I. Occurrence in higher plants.

              Shoots, roots, and seeds of corn (Zea mays L., cv. Michigan 500), oats (Avena sativa L., cv. Au Sable), and peas (Pisum sativum L., cv. Wando) were analyzed for their superoxide dismutase content using a photochemical assay system consisting of methionine, riboflavin, and p-nitro blue tetrazolium. The enzyme is present in the shoots, roots, and seeds of the three species. On a dry weight basis, shoots contain more enzyme than roots. In seeds, the enzyme is present in both the embryo and the storage tissue. Electrophoresis indicated a total of 10 distinct forms of the enzyme. Corn contained seven of these forms and oats three. Peas contained one of the corn and two of the oat enzymes. Nine of the enzyme activities were eliminated with cyanide treatment suggesting that they may be cupro-zinc enzymes, whereas one was cyanide-resistant and may be a manganese enzyme. Some of the leaf superoxide dismutases were found primarily in mitochondria or chloroplasts. Peroxidases at high concentrations interfere with the assay. In test tube assays of crude extracts from seedlings, the interference was negligible. On gels, however, peroxidases may account for two of the 10 superoxide dismutase forms.

                Author and article information

                Planta Daninha
                Planta daninha
                Sociedade Brasileira da Ciência das Plantas Daninhas (Viçosa, MG, Brazil )
                : 21
                : spe
                : 27-35
                Botucatu SP orgnameIB-UNESP orgdiv1Instituto de Biociências orgdiv2Departamento de Botânica
                Botucatu SP orgnameFCA-UNESP orgdiv1Faculdade de Ciências Agronômicas orgdiv2Departamento de Produção Vegetal - setor Agricultura eacorrea@ 123456fca.unesp.br
                Botucatu SP orgnameUNESP orgdiv1Instituto de Biociências orgdiv2Departamento de Química e Bioquímica
                orgnameIB-UNESP orgdiv1Departamento de Botânica orgdiv2Programa de Pós-Graduação em Botânica
                S0100-83582003000400005 S0100-8358(03)02100005

                This work is licensed under a Creative Commons Attribution 4.0 International License.

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