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
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.
Aquatic macrophytes are potentially useful for phytoremediation programmes in environments contaminated by arsenic (As). Biochemical and physiological modification analyses in different plant parts are important to understand As tolerance mechanisms. The objective was to evaluate glutathione metabolism in leaves and roots of Eichhornia crassipes (Mart.) Solms treated to As. Specimens of E. crassipes were cultured for 3 days in Clark's nutrient solution containing 7 μm As. The enzymes ATP sulphurylase (ATPS), glutathione reductase (GR), glutathione peroxidase (GSH‐Px), glutathione sulphotransferase (GST) and γ‐glutamylcysteine synthetase (γ‐ECS) activity, glutathione content, total protein and non‐protein thiols were evaluated. The ATPS activity increased in roots. GR activity in leaves and GSH‐Px in roots were lower. GST activity was higher in roots and lower in leaves, and γ‐ECS activity was higher in leaves. Glutathione levels were lower, total thiol levels were higher and non‐protein levels did not change in E. crassipes leaves and roots. Exposure to As increased enzyme activity involved with sulphur metabolism, such as ATPS. Higher GR activity and lower GSH‐Px indicate increased glutathione conjugation to As due to increased GSH availability. The higher GST activity indicates its participation in As detoxification and accumulation through As GSH conjugation. Changes in glutathione and thiol levels suggest high phytochelatin synthesis. In conclusion, the increments in ATPS, GR, GST and γ‐ECS activity indicate that these enzymes are involved in GSH metabolism and are part of the E. crassipes As detoxification mechanism.
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