The freshwater wetland plants, Echinochloa crusgalli crusgalli and Echinochloa crusgalli zelayensis, and the saltmarsh plant Spartina alterniflora were exposed to the herbicides metolachlor and norflurazon in two types of toxicity tests: (1) seed germination and early seedling growth in water, and (2) seedling survival and growth in natural and synthetic sediments. The synthetic sediments were formulated to be similar to the natural sediments with regard to particle size distribution and organic content. The herbicides did not affect rate of germination, but significantly inhibited rate of early growth and survival and rate of growth of older seedlings in sediments. Echinochloa was more sensitive than Spartina to both herbicides. Inhibition of the growth rates of the two varieties of E. crusgalli was similar in natural and synthetic sediments, but inhibition of growth of S. alterniflora was greater in synthetic than in natural sediment. It is concluded that the species tested may be used for estimation of potential effects of toxicants on wetland plants and that synthetic sediments of known composition may be used in sediment toxicity tests.
RESUMO -As microalgas tem despertado cada vez mais atenção pela sua capacidade em sintetizar inúmeros metabólitos bioativos de interesse. Nesse sentido, o objetivo do trabalho foi avaliar o conteúdo fenólico bem como o potencial antioxidante de Scenedesmus obliquus CPCC05 e Phormidium autmnalle. As biomassas foram produzidas em fotobiorreator de coluna de bolhas acoplado a uma plataforma de iluminação, operando de forma intermitente com alimentação de 1,5 L de meio BG11, concentração inicial de inoculo de 100 mg.L -1 , temperatura de 25 ºC, aeração de 1 volume de ar por volume de meio por minuto (VVM) através da injeção de ar enriquecido com 15,0% de dióxido de carbono (v/v), a relação volume de meio circundante na plataforma de iluminação e área escura foi de 20% e intensidade luminosa de 13000 Lux. O conteúdo fenólico foi extraído das biomassas por meio de agitação orbital com metanol e determinado através de reagente de Folin-Ciocalteu. A atividade antioxidante foi estabelecida através da capacidade do extrato fenólico em desativar espécies reativas de oxigênio. Com base nos resultados obtidos, a microalga Scenedesmus obliquus CPCC05 apresentou maior conteúdo fenólico total (871,2 µg EAG.g -1 ) bem como maior potencial antioxidante (23,5 µMol TE.g -1 ) em relação a Phormidium autumnale (552,6 µg EAG.g -1 e 16,3 µMol TE.g -1 ). Deste modo, sugere-se que essa microalga pode ser explorada como uma via natural de produção compostos fenólicos.
Sediments and rooted aquatic plants are major components of wetland systems. Sediments in these systems act as sinks and reservoirs for organic and inorganic pollutants that are adsorbed to sediment particles or contained in interstitial water that exists between the particle spaces of sediments. Sediments may release toxic materials to aquatic environments through processes that include resuspension, desorption, and bioturbation. In sediment systems, aquatic plants are affected by toxic materials through direct effects on root growth or rhizosphere microorganisms, or by the assimilation and translocation of chemical substances to aerial organs, where they may injure foliage or inhibit growth and seed production. Procedures are being developed to identify the effects of contaminated sediments on aquatic plants through use of laboratory toxicity tests involving natural and artificial sediments, and a group of rooted aquatic species. In these studies, two freshwater species, Echinochloa crusqalli and Sesbania macrocarpa, and a saltmarsh species, Spartina alterniflora, are being evaluated. Artificial substrates proved useful in assessing the effects of contaminants on plant growth and development, and provided techniques for evaluating the role of sediment components on plant response.
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