RESUMOMetabótitos secundários produzidos em algumas plantas podem provocar alterações no desenvolvimento de outras plantas ou até mesmo de outros organismos. Neste trabalho, objetivou-se identificar possíveis efeitos alelopáticos de extratos aquosos de folhas de Cyperus rotundus na germinação e no crescimento de plântulas de Brassica campestris, Brassica oleracea var. botrytis, Brassica oleracea var. capitata, Brassica oleracea var. italica, Brassica rapa, Lactuca sativa cv. Grand rapids, Lycopersicum esculentum e Raphanus sativus. Foram utilizadas sete concentrações do extrato aquoso (0, 10, 30, 50, 70, 90 e 100%). Os tratamentos foram arranjados em delineamento inteiramente casualizado, com cinco repetições de dez sementes das espécies cultivadas, constituindo a unidade amostral. Os extratos aquosos de C. rotundus evidenciaram potencialidades alelopáticas na germinação das sementes e no crescimento das duas partes vegetais (raiz e parte aérea), de todas as espécies testadas, exceto na germinação de sementes de tomate e de alface, sendo que a redução aumentou com o aumento das concentrações dos extratos aquosos utilizados. A estrutura vegetal mais afetada em presença dos extratos aquosos foi o sistema radicular das plântulas.Termos para indexação: Alelopatia, Germinação de sementes, Crescimento. ABSTRACTSecondary metabolites produced in some plant species may promote changes in the development of other plants or even in other organisms. The aim of this work was to identify the possible allelopathic effects of aqueous extracts of Cyperus rotundus leaves on germination and growth of Brassica campestris, Brassica oleracea var. botrytis, Brassica oleracea var. capitata, Brassica oleracea var. italica, Brassica rapa, Lactuca sativa cv. Grand rapids, Lycopersicum esculentum and Raphanus sativus seedlings. Seven aqueous extract concentrations were used (0, 10, 30, 50, 70, 90, and 100%). The treatments were arranged in a completely randomized desing, with five replications of ten seeds of each cultivated species constituting the sample unity. The aqueous extracts of C. rotundus revealed allelopathic potentialities on germination of seeds and growth of two vegetable parts (root and aerial part) of all tested species, except on germination of L. sativa and L. esculentum seeds, being that the reduction increased with the increase of the aqueous concentration extracts which were used. The seedlings roots were the most affected structure in the presence of aqueous extracts.Index terms: Allelopathy, seed germination, growth. (Recebido em 16 de maio de 2007 e aprovado em 29 de abril de 2008)Os aleloquímicos, biomoléculas responsáveis pelos efeitos alelopáticos, são produtos naturais que podem ser metabólitos diretos, subprodutos de outros processos metabólicos ou produtos da decomposição de compostos ou biomassa. São freqüentemente nocivos para a planta que produz, se não forem armazenados numa forma não tóxica ou liberados antes de se acumularem internamente até atingirem níveis tóxicos (GLIESSMAN, 2000).

The objective of this study was to evaluate the concentration of potentially toxic elements in Brachiaria decumbens, Stylosanthes guianensis, and Saccharum officinarum plants and soil samples in affected and unaffected areas by rupture of the Fundão dam, Brazil. Samples were collected in areas affected by residues from the Fundão dam (RAA1, RAA2, RAA3) and in an unaffected area (control). The material was analyzed for the composition of micronutrients and trace elements in soil and plants, as well as contamination factor (CF), accumulation factor, and translocation factor (TF). Overall, the results showed that soil and plant tissues had increased Fe, Mn, Cu, and Cr content and decreased Zn content in the affected areas, compared to the control. Leaves and roots of B. decumbens showed an increase in Fe content in affected areas, compared to the control, reaching a mean maximum value of 42 958 µg/g of roots of RAA2‐collected plants. As a result, CF for Fe of B. decumbens was classified as very high and they presented low TF values. Furthermore, B. decumbens collected in affected areas showed an increase of Fe, Mn, Cu, and Cr in leaves, stems, and roots, whereas in Stylosanthes guianensis, there was an increase of Fe concentration in all tissues and Cr in leaves. Also, Saccharum officinarum showed the accumulation of Mn in the stem and Cu in leaves and stem. On the other hand, there was no contamination of plants by hazardous elements such as Pb, Cd, and As in the samples analyzed. In conclusion, increases in the content of Fe, Mn, Cu, and Cr were found in soil and several plant tissues of residue‐affected areas, which could compromise plant growth and represent potential hazards arising from the biomagnification process in the food chain. Integr Environ Assess Manag 2020;16:596–607. © 2020 SETAC

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Oxidative damage is one of the most harmful effects arising from arsenic (As) toxicity in plants. Herein, the role of exogenous jasmonic acid (JA) in the modulation of As-induced oxidative stress in Lemna valdiviana was investigated. Plants were grown for 24 h in Clark's nutritive solution containing As (4.0 mg L −1) or As + JA (50, 100, 250 and 500 µM). Chlorophyll a and b content decreased under As stress, either in isolation or associated with JA. The decreased chlorophyll a/b ratio in As-exposed plants was recovered by JA treatment at 100 µM. The carotenoid content was higher in plants exposed to As compared to controls and lower when it was associated with JA. Arsenic triggered the accumulation of O 2 •− and H 2 O 2 , in addition to severely increasing lipid peroxidation. Application of JA in As-grown plants resulted in lower O 2 •− content and lipid peroxidation than in those grown under As alone, as a result of enhanced SOD activity. On the other hand, H 2 O 2 accumulation was increased by JA in As-stressed plants, associated with higher CAT, POX and GPX activity. The As content and bioaccumulation factor (BF) were improved by application of JA in the nutritive solution at 250 and 500 µM. Our findings indicate that JA modulates the pigment balance, thereby fine-tuning energy dissipation as well as alleviating As-induced oxidative damage in L. valdiviana through modulation of ROS homeostasis and improvement of the antioxidant enzymatic system, allowing increased accumulation of As without showing major damage.