RESUMO
The herbicide glyphosate can cause severe ecotoxicological effects on non-target organisms. Eugenia uniflora L. (Myrtaceae) is very important for in situ environmental biomonitoring due to its wide distribution in the Atlantic Forest biome. Thus, this study aimed to evaluate the response of E. uniflora leaves to glyphosate. Eight-month-old plants were exposed to an aerial application of the herbicide at concentrations of 0, 144, 432, 864, and 1440 g a. e. ha-1 (grams of acid equivalent per hectare). Evaluations were performed on the 12th day after the glyphosate application (DAA). An accumulation of shikimic acid in the leaves of E. uniflora was observed. Glyphosate altered the photosynthetic parameters of the treated plants, with a drastic decrease in the photosynthetic rate, stomatal conductance, transpiration, and pigment content. There was an increase in Ci/Ca, lipid peroxidation, and electrolyte extravasation levels. Glyphosate also promoted ultrastructural, anatomical and visible damage to the E. uniflora leaves. Our findings indicate that glyphosate is phytotoxic to the native species E. uniflora at the tested doses. The presence of visible damage suggests that E. uniflora has remarkable potential as a bioindicator of glyphosate in the environment, making it a possible species for future biomonitoring projects.
Assuntos
Eugenia , Hepatite C Crônica , Herbicidas , Brasil , Ecossistema , Florestas , Glicina/análogos & derivados , Herbicidas/toxicidade , Folhas de Planta , GlifosatoRESUMO
Pityrogramma calomelanos is interestingly the single non-Pteris arsenic (As)-hyperaccumulating fern. It has been pointed as a potential species for phytoremediation and a model plant to study the As toxicity and its mechanisms of action. In order to investigate the morphoanatomical traits associated to As tolerance, P. calomelanos plants were exposed to different As concentrations in hydroponic solution. At low As dose (1 mM As), 90% of the As accumulated in plants was allocated in shoots, and no symptoms of As stress were observed in fronds and roots. Under higher As exposure (10 and 30 mM As), 81-74% of the total As in plants was present in shoots, and apical and marginal necroses on pinnae were observed. Anatomical observations showed that As induces damages mainly in the secondary veins and adjacent cells. High amounts of phenols were observed in pinna tissues of control and treated plants. In the roots, As promoted slight alterations as detachment of border-like cells and accumulation of granular substances in cortical cells. The high root-to-shoot As translocation and the constitutive presence of phenols and border-like cells protecting the root tips showed to be adaptive traits that allow P. calomelanos to survive in contaminated sites.
Assuntos
Arsênio/análise , Gleiquênias/química , Poluentes do Solo/análise , Biodegradação AmbientalRESUMO
Glyphosate is a broad-spectrum systemic herbicide used worldwide. In susceptible plants, glyphosate affects the shikimate pathway and reduces aromatic amino acid synthesis. Using Arabidopsis seedlings grown in the presence of 20µM glyphosate, we analyzed H2O2, ascorbate, glutathione (GSH) and protein oxidation content as well as antioxidant catalase, superoxide dismutase (SOD) and ascorbate-glutathione cycle enzyme activity. We also examined the principal NADPH-generating system components, including glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), NADP-malic enzyme (NADP-ME) and NADP-isocitrate dehydrogenase (NADP-ICDH). Glyphosate caused a drastic reduction in growth parameters and an increase in protein oxidation. The herbicide also resulted in an overall increase in GSH content, antioxidant enzyme activity (catalase and all enzymatic components of the ascorbate-glutathione cycle) in addition to the two oxidative phase enzymes, G6PDH and 6PGDH, in the pentose phosphate pathway involved in NADPH generation. In this study, we provide new evidence on the participation of G6PDH and 6PGDH in the response to oxidative stress induced by glyphosate in Arabidopsis, in which peroxisomal enzymes, such as catalase and glycolate oxidase, are positively affected. We suggest that the NADPH provided by the oxidative phase of the pentose phosphate pathway (OxPPP) should serve to maintain glutathione reductase (GR) activity, thus preserving and regenerating the intracellular GSH pool under glyphosate-induced stress. It is particularly remarkable that the 6PGDH activity was unaffected by pro-oxidant and nitrating molecules such as H202, nitric oxide or peroxynitrite.
Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/efeitos dos fármacos , Glicina/análogos & derivados , Herbicidas/toxicidade , NADP/metabolismo , Estresse Oxidativo , Peroxissomos/metabolismo , Antioxidantes/metabolismo , Arabidopsis/enzimologia , Arabidopsis/metabolismo , Glicina/toxicidade , Via de Pentose Fosfato/efeitos dos fármacos , Peroxissomos/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Plântula/efeitos dos fármacos , Plântula/metabolismo , GlifosatoRESUMO
Arsenic (As) pollution is a major environmental concern due to its worldwide distribution and high toxicity to organisms. The fern Pityrogramma calomelanos is one of the few plant species known to be able to hyperaccumulate As, although the mechanisms involved are largely unknown. This study aimed to investigate the metabolic adjustments involved in the As-tolerance of P. calomelanos. For this purpose, ferns with five to seven fronds were exposed to a series of As concentrations. Young fronds were used for biochemical analysis and metabolite profiling using gas chromatography-mass spectrometry. As treatment increased the total concentration of proteins and soluble phenols, enhanced peroxidase activities, and promoted disturbances in nitrogen and carbon metabolism. The reduction of the glucose pool was one of the striking responses to As. Remarkable changes in amino acids levels were observed in As-treated plants, including those related to biosynthesis of glutathione and phenols, osmoregulation and two photorespiratory intermediates. In addition, increases in polyamines levels and antioxidant enzyme activities were observed. In summary, this study indicates that P. calomelanos tolerates high concentration of As due to its capacity to upregulate biosynthesis of amino acids and antioxidants, without greatly disturbing central carbon metabolism. At extremely high As concentrations, however, this protective mechanism fails to block reactive oxygen species production, leading to lipid peroxidation and leaf necrosis.
Assuntos
Arsênio/metabolismo , Pteridaceae/fisiologia , Estresse Fisiológico , Aminoácidos/biossíntese , Antioxidantes/metabolismo , Arsênio/toxicidade , Biodegradação Ambiental , Biomarcadores/metabolismo , Vias Biossintéticas/efeitos dos fármacos , Cromatografia Gasosa-Espectrometria de Massas , Estresse Oxidativo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/fisiologia , Pteridaceae/efeitos dos fármacos , Poluentes do Solo/metabolismo , Poluentes do Solo/toxicidadeRESUMO
We wished to evaluate the effects of arsenic on the morphology and anatomy of Brassica oleracea, Raphanus sativus, Brassica juncea, Brassica oleracea var. capitata and Brassica oleracea var. italica. Seeds were subjected to concentrations 0µM, 250µM, 350µM and 450µM arsenic in the form of sodium arsenate (Na2HAsO4·7H2O) during 12 days. All species accumulated more arsenic in the roots than in the shoots, except for B. oleracea var. capitata. There was no difference of translocation factor between species and treatments. Growth decrease was observed in roots of B. oleracea and R. sativus, and in shoots of R. sativus and B. oleracea var. italica. All species presented anatomical alterations in the roots, such as: cell hypertrophy, protoplast retraction, cellular plasmolysis, and necrotic regions. B. juncea presented collapse and hypertrophy of cells from the leaf blade tissues. Quantitative anatomical analyses performed on the root and leaves of B. oleracea and B. juncea revealed that arsenic interfered on the root vascular cylinder diameter and on height of epidermal cells of the adaxial leaf surface of both species. We concluded that arsenic was absorbed from the culture medium and induced alterations both on root and shoot growth of the seedlings. Retention of arsenic within the root was responsible for major damage in this organ.
Assuntos
Arsênio/farmacologia , Arsênio/toxicidade , Mostardeira/efeitos dos fármacos , Mostardeira/crescimento & desenvolvimento , Mostardeira/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/crescimento & desenvolvimento , Folhas de Planta/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/crescimento & desenvolvimento , Raízes de Plantas/metabolismo , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/crescimento & desenvolvimento , Brotos de Planta/metabolismo , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Plântula/metabolismo , Sementes/efeitos dos fármacos , Sementes/crescimento & desenvolvimento , Sementes/metabolismoRESUMO
We aimed to verify whether morphoanatomic alterations occur in response to excess iron, in roots of Setaria parviflora and Paspallum urvillei (Poaceae), and to localize the presence of the sites of iron accumulation. Plants were subjected to 0.009, 1, 2, 4, and 7 mM Fe-EDTA in nutrient solution. Both species presented iron contents in the roots above the critical toxicity level. The presence of iron plaque on roots of the two species was confirmed, and it may have reduced iron absorption by the plants. Roots from the two species showed typical visual symptoms of stress by excess iron: change in color and mucilaginous and flaccid appearance. Anatomical damage was observed in both species: aerenchyma disruption, alterations in endodermal cells, and irregular shape of both vessel and sieve tube elements. The metal was histolocalized in the cortex and in protoxylem and metaxylem cell walls in both species, which suggests a detoxification strategy for the excess iron. Phenolic compounds were not histolocalized in roots. Microscopic analyses were therefore effective in evaluating the real damage caused by excess iron.
Assuntos
Ferro/toxicidade , Paspalum/efeitos dos fármacos , Raízes de Plantas/efeitos dos fármacos , Setaria (Planta)/efeitos dos fármacos , Parede Celular/metabolismo , Ferro/metabolismo , Metais , Microscopia Eletrônica de Varredura , Paspalum/metabolismo , Paspalum/ultraestrutura , Raízes de Plantas/metabolismo , Raízes de Plantas/ultraestrutura , Plantas , Poaceae , Setaria (Planta)/metabolismo , Setaria (Planta)/ultraestruturaRESUMO
Setaria parviflora (Poir.) Kerguélen and Paspalum urvillei Steudel are grasses that grow naturally in a soil with high iron contents. This study aimed to characterize morphoanatomically and histochemically the iron phytotoxicity on leaves and evaluate the phytoextraction potential of these grasses. Saplings were cultivated in hydroponic solution with and without excess Fe-EDTA. Regarding measurements taken on leaves, reduction was observed among treatments of Fe-EDTA on height values of abaxial epidermis and bundle sheath in both species. As for iron histolocalization, stronger reaction was observed in leaves of S. parviflora, in comparison with P. urvillei. Anatomical damage, such as protoplast retraction, irregular xylem, changes in cell volume, and cell collapse, and visual symptoms, like leaf bronzing, chlorosis, and necrosis, were similar in both species when exposed to excess iron; however, P. urvillei showed more severe damage. This species accumulated more iron in shoots than S. parviflora and therefore is more favorable for use in phytoextraction. The root system of both species accumulated higher iron concentrations in relation to shoots.
Assuntos
Ferro/toxicidade , Paspalum/efeitos dos fármacos , Setaria (Planta)/efeitos dos fármacos , Biodegradação Ambiental , Ferro/metabolismo , Paspalum/anatomia & histologia , Paspalum/metabolismo , Folhas de Planta/anatomia & histologia , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Brotos de Planta/metabolismo , Setaria (Planta)/anatomia & histologia , Setaria (Planta)/metabolismoRESUMO
This study aimed to assess the influence of excess iron on the capacity of accumulation of this heavy metal, mineral composition, and growth of Setaria parviflora and Paspalum urvillei. Seedlings were submitted to 0.009; 1; 2; 4; and 7 mM of Fe-EDTA. In both species there was an increase in the concentration of Fe, Zn, P, and Ca and a decrease in Mn, K, and Mg in the iron plaque. Both species accumulated more iron in roots. In the shoots, S. parviflora showed higher iron content, except at 7 mM. Iron altered the contents of Fe, Cu, K, and Mg in roots, and of Fe, Mn, Zn, N, P, K, Ca, and Mg in shoots. The two species tolerated high iron concentrations and accumulated high content of this element in both shoots and roots. The iron did not reduce their growth. Both species are indicated for studies aiming restoration of iron-contaminated areas.