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Chemical weed control is essential to ensure high levels of productivity in agricultural areas, and glyphosate-based herbicides (GBHs) are the most widely used herbicides on a global scale. Glyphosate-based herbicides inhibit the 5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS) enzyme, which impairs the shikimate pathway and often leads to plant death. However, indirect effects of GBHs on plant physiology can also lead to plant death. The objectives of this review are to discuss the biochemical, physiological, and structural changes that GBH application produces in plant species, in addition to inhibiting EPSPS (EC 2.5.1.19), and to reveal how these changes contribute to plant death. We conclude that GBHs promote plant death not only through EPSPS inhibition but also through biochemical, physiological, and structural changes. Some changes are recurrent and can be used as biomarkers of GBH sensitivity, which can contribute to future works that monitor the presence of these herbicides in plant communities near agricultural areas.

In acidic soil, aluminum (Al) ionizes into trivalent cation and becomes highly toxic to plants. Thus, the objectives of this work were (i) to evaluate the Al concentration and identify sites of Al toxicity and its effect on the structure on rice root tips and (ii) to elucidate the adjustments involved in the activities/contents of enzymes/compounds in the roots against Al. For this, two genotypes with contrasting Al tolerance were used. Our results showed that the root length of the tolerant genotype was not affected after Al exposure. We also observed that both the genotypes used strategies to avoid Al uptake, such as the overlap of P and Al in the tolerant genotype and the presence of border cells in the sensitive genotype, which proved inefficient. In the tolerant genotype, other external Al detoxification mechanisms may have contributed to the lower Al concentration in roots and lower fluorescence of the Al-lumogallion complex. Additionally, both genotypes present the activation of key enzymes to decrease oxidative stress, such as CAT, POX, APX, and DHAR, and a more reducing redox environment, mainly due to the increase in the AA/DHA ratio. However, higher total ascorbate, AA, total glutathione, and GSH contents associated with higher SOD, GPX, and GR activities contributed to the reduction of oxidative stress in the tolerant genotype after Al exposure. Furthermore, there was a strong association between the sensitive genotype to Al concentration, O

When glyphosate is applied, some of the herbicide can reach adjacent vegetation and impact the natural plant community structure and diversity over the long term. This study evaluated the response of leaves of Zeyheria tuberculosa (Vell.) Bureau ex Verl. (Bignoniaceae) to the herbicide glyphosate. Plants were exposed to aerial applications of the herbicide at concentrations of 0, 360, 720, 1080, or 1440 g acid equivalent (a.e.)·ha−1. The concentrations of shikimic acid in leaves of the herbicide-treated plants were always higher than the controls. Visual symptoms became apparent four days after the application of 720 g·ha−1. Glyphosate induced an increase in malondialdehyde in Z. tuberculosa leaves. The lowest levels of chlorophyll a were found for the three last applied doses, and protein content decreased with the glyphosate treatment. Necrosis was observed on the epidermis and in the mesophyll. Glandular trichomes were also plasmolyzed. On the midrib there was plasmolysis of non-lignified cells. Micromorphologically, there were cell plasmolysis and rupture of glandular trichomes. Thus, glyphosate is phytotoxic to Z. tuberculosa by causing biochemical, anatomical, and morphological changes. The morphoanatomical injuries found on Z. tuberculosa were severe, suggesting that the presence of glyphosate can irreversibly affect this species and compromise its survival.

Rutaceae species, especially of the genus Zanthoxylum L., are known for possessing a well-diversified chemical composition with high potential for pharmacological activity. A variety of Zanthoxylum species are distributed throughout Brazil. This study aimed to characterize the leaf anatomy and identify the histochemical composition of the secretory material from the secretory structures of Z. caribaeum leaves. Leaves of Z. caribaeum were collected and processed for anatomical, histochemical and micromorphological characterization following standard methodologies. The leaves have an unstratified epidermis and glandular trichomes in epidermal depressions on the abaxial surface. Extrafloral nectaries were also observed on the abaxial surface. The leaf is hypostomatic and the stomata are anomocytic. The mesophyll is dorsiventral and has secretory cavities. The mesophyll cavities produce a secretion of lipidic nature and the cavities on the leaf margin produce a secretion of mixed nature, with neutral lipids and essences. In summary, our findings show that the leaves of Z. caribaeum have secretory structures like glandular trichomes that can function as extrafloral nectaries and cavities. The characterization of the leaf anatomy of Z. caribaeum can provide relevant data for future taxonomic studies of the genus.

Potassium (K

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.

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.

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 20 μM 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.

An iron ore pelletizing plant in southeastern Brazil exposes the tropical coastal ecosystems known as restinga to emissions of dust, iron solid particulate matter, and sulfur dioxide (SO2). We aimed to assess the effects of those emissions on the leaf morphology and anatomy of the restinga species Byrsonima sericea, Cordia verbenacea, and Psidium guineense by evaluating visual symptomatology and analyzing the anatomical and micromorphological alterations resulting from exposure. Leaves were collected from individuals growing at two sites: a restinga forest fragment located 800 m away from the pelletizing plant and a restinga conservation unit 20 km away, which served as reference site. In all three species, individuals growing near the pelletizing plant showed necrotic regions on the leaf and foliar micromorphological alterations like turgor loss of epidermal cells, cuticle and epicuticular wax erosion, stomatal obliteration, and rupture and plasmolysis of trichomes. Anatomically, we found cell collapse, cell hypertrophy, and formation of a wound tissue. C. verbenacea showed the most severe visual and anatomical damage, being thus considered the most sensitive species to emissions. Leaf structural features such as uniseriate epidermis, lack of hypodermis, and presence of trichomes contributed to the highest sensitivity of C. verbenacea. Our findings reinforce the importance of performing morpho-anatomical studies to elucidate how leaf structure determines differential sensitivity to airborne pollutants in native species.

The use of aerial spraying herbicide in large areas is common in Brazil, especially glyphosate, which is the most extensively used herbicide worldwide. A portion of the herbicide can reach non-target species, resulting in damage in these species and causing severe implications for the local biodiversity. Thus, this study aimed to evaluate the responses of the leaves of Handroanthus chrysotricus (Mart. Ex DC) Mattos (Bignoniaceae) and Garcinia gardneriana (Planch. & Triana) Zappi (Clusiaceae) to glyphosate and its potential for biomonitoring purposes, seeking to establish biomarkers that could indicate the effects of the herbicide in its foliar tissues. Eight months old plants were exposed to the aerial application of herbicide in the concentrations of 0, 360, 720, 1080 and 1440 g. a.i. ha−1. An accumulation of shikimic acid in the leaves of both species was observed. H. chrysotrichus displayed a drastic decrease in A, gs, E, Fv/Fm, Qp, NPQ and ETR and an increase in MDA, POX glucose, fructose, sucrose and chlorophyll a values whereas G. gardneriana displayed greater activity on CAT, APX, SOD, GR and an increase in starch, amino acids and fumarate values. Visible damages were found only in H. chrysotrichus, whereas anatomical and ultrastructural damages were observed in both species. H. chrysotrichus was considered the most sensitive species of this work because it presented more pronounced alterations. The presence of visible damages suggests that H. chrysotricus has remarkable potential as a bioindicator of glyphosate presence in the environment. Shikimic acid accumulation and photosynthesis disruption can be used as biomarkers for glyphosate presence in its leaf’s tissues. The anatomical damages and the increase of enzymatic antioxidative system activity can indicate the glyphosate presence in G. gardneriana leaves.

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 0 µM, 250 µM, 350 µM and 450 µM 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

6-Phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) catalyzes the third and irreversible reaction of the pentose phosphate pathway (PPP). It carries out the oxidative decarboxylation of the 6-phosphogluconate to yield ribulose-5-phosphate, carbon dioxide and NADPH. In higher plants, 6PGDH has several subcellular localizations including cytosol, chloroplast, mitochondria and peroxisomes ( Corpas et al., 1998 ; Krepinsky et al., 2001 ; Mateos et al., 2009 ; Fernandez-Fernandez and Corpas, 2016; Holscher et al., 2016 ). Using Arabidopsis thaliana as plant model and sweet pepper (Capsicum annuum L.) fruits as a plant with agronomical interest, this protocol illustrates how to prepare the plant extracts for the separation of the potential 6PGDH isoforms by electrophoresis on 6% polyacrylamide non-denaturing gels. Thus, this method allows detecting three 6PGDH isoforms in Arabidopsis seedlings and two 6PGDH isoforms in sweet pepper fruits.

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.

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.

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.

O objetivo deste trabalho foi avaliar o efeito do silício (Si) no processo infeccioso de Phakopsora pachyrhizi em folíolos de soja cultivada em solução nutritiva com ou sem Si. Observações realizadas sob microscópio de luz e microscópio eletrônico de varredura indicaram que, nos folíolos das plantas supridas com Si, as urédias foram menores e em menor número. Houve redução de 27, 23 e 60% no número de lesões, urédias fechadas e urédias abertas, respectivamente, nos folíolos das plantas com Si. Plantas de soja supridas com Si apresentam redução nos sintomas da ferrugem-asiática-da-soja. The objective of this work was to evaluate the effect of silicon (Si) on the infection process of Phakopsora pachyrhizi in leaflets of soybean plants grown in nutrient solution with or without Si. Observations done with light microscope and scanning electron microscope indicated that, in leaflets of plants supplied with Si, uredia were smaller and fewer in number. There were reductions of 27, 23 and 60% in the number of lesions, closed uredia and open uredia, respectively, in leaflets of plants with Si. Soybean plants supplied with Si show reduction in Asian soybean rust symptoms.

Dada a importância do pepino (Cucumis sativus L.), destacando-se entre as hortaliças pelo alto consumo, aliada à escassez de pesquisas que relatem sintomatologias de desordens nutricionais na cultura, realizou-se o trabalho com o objetivo de avaliar o efeito da omissão de nutrientes nos aspectos morfológicos e anatômicos do pepino. O experimento, realizado em sistema hidropônico, foi conduzido em casa de vegetação do Departamento de Agronomia da Universidade Federal de Viçosa, MG. O delineamento experimental empregado foi o inteiramente ao acaso com cinco tratamentos: solução completa, 30% do N recomendado para a cultura, omissão de Mg, S e Fe, com quatro repetições, com uma unidade experimental sendo representada por um vaso com uma planta. Avaliou-se altura de plantas, diâmetro do caule, número de folhas, área foliar, massa seca da parte aérea, massa seca de raiz e volume de raiz, além da descrição anatômica e morfológica e registro fotográfico dos sintomas de deficiências aliados a omissão dos nutrientes na solução. O tratamento com omissão total de Fe foi aquele que mais limitou a produção de todas as variáveis avaliadas. Foi possível observar, registrar e descrever os sintomas de deficiência de todos os nutrientes omitidos da solução durante o crescimento inicial das plantas de pepino. As plantas de pepino deficientes de um ou mais nutrientes apresentaram sintomas específicos, os quais estão intimamente relacionados à desorganização de seus tecidos constituintes.