Hydrogen peroxide, superoxide, lipid peroxidation and membrane damage in leaves of the tree Prosopis nigra (Fabaceae) under simulated glyphosate drift

Introduction: The tree Prosopis nigra is native to the Western Chaco phytogeographic region, affected by the application of glyphosate in the surrounding crops. Objective: To determine the impact of simulated glyphosate drift on growth, photosynthesis and oxidative stress in P. nigra seedlings. Methods: We simulated drift in seedlings at doses of 0, 200, 400 and 800 g a.e. ha-1 of glyphosate. We also measured gas exchange and modulated fluorescence emission of chlorophyll a. Results: Glyphosate reduced biomass, photosynthetic rate, and stomatal conductance. Doses of 400 and 800 g a.e. ha-1 glyphosate produced photoinhibition. The electron transport rate was sensitive to glyphosate, and it decreased at all doses of the herbicide. Glyphosate generated oxidative stress, and produced damage to membranes, because of the accumulation of H2O2 and O2.. Conclusions: Glyphosate reduces growth and photosynthesis in these seedlings. The inhibition of photosynthesis is due to stomatal closure, and alterations in the photochemical stage, associated with oxidative stress.

Effect of glyphosate drift on marandu grass

Glyphosate drift in plants that are not resistant to the herbicide molecule can result in stimulation to certain biological features, characterizing the phenomenon of hormesis. On this basis, productive and chemical traits were evaluated in marandu grass, in a simulation of the drift effect, using sublethal doses of the herbicide glyphosate. The experiment was in laid out in a randomized-block design with split plots in time, in four replicates. The effect of sublethal doses of glyphosate acid equivalent (a.e.) (21.60, 43.20, 64.80, 86.40 and 108.00 g ha-1) and control was evaluated in the plots; and the effect of harvesting at 92, 113, 134 and 155 days after sowing (DAS) the grass was evaluated in the subplots. The Urochloa brizantha cv. Marandu was collected at a height of 0.20 m, at a defoliation interval of 21 days, to estimate production and chemical traits, in experimental plots with a usable area of 7.5 m2. Leaf: stem ratio was influenced by the interaction between the evaluated factors (dose and harvest). Dose fitted a second-order polynomial model, with a hormesis effect of 21.60 to 76.50 g ha-1 of glyphosate a.e. Harvesting at 134 DAS differed significantly from 92 DAS. The forage yield showed a linear response inversely proportional to the increasing glyphosate doses. There was a polynomial increase in leaf phosphorus content, characterizing hormesis up to the sublethal dose of 72.50 g a.e. ha-1. Harvest influenced the neutral detergent fiber, acid detergent fiber, lignin and leaf phosphorus contents.

PHYSIOLOGICAL RESPONSES OF Eucalyptus camaldulensis (Dehnh.) TO SIMULATED GLYPHOSATE DRIFT

Weed control with glyphosate produces damages in plantations of Eucalyptus camaldulensis, although the involved physiological mechanisms have not been completely elucidated. This work aimed at assessing the physiological responses of E. camaldulensis to simulated glyphosate drift. Greenhouse trials were performed with four-month-old E. camaldulensis clone117 seedlings. The herbicide drift was simulated applying doses of 0; 43,2; 86,4; 172,8 and 345,6 g a.e. ha−1 glyphosate. Twenty-three days after the application, we measured gas exchange and chlorophyll a fluorescence. We also quantified Rubisco activity and indicator variables of oxidative stress. Glyphosate decreased carbon photosynthetic assimilation, increased non-photochemical quenching, induced stomatal closure, and increased photoinhibition. It also decreased Rubisco activity and increased photorespiration. The herbicide produced oxidative stress, and increased the activities in the enzymes catalase, ascorbate peroxidase, and superoxide dismutase, involved in the detoxification of reactive oxygen species. We concluded that glyphosate´s deleterious effects on the assimilation of CO2 in E. camaldulensis are due to stomatal and non-stomatal effects. The decrease in Rubisco activity, the increase in photorespiration, and photoinhibition stand out among non-stomatal effects. The increase in the activity of the antioxidant system is insufficient to compensate for the production of H2O2 in photorespiration, which damages the photosynthetic apparatus.

Morphoanatomical and biochemical changes in Zeyheria tuberculosa exposed to glyphosate drift

During glyphosate application, a portion 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 and 1440 g a. e. ha-1. The shikimic acid concentrations in leaves of herbicide-treated plants were always higher than the control. Visual symptoms became apparent 4 DAA from 720 g a. e. ha-1. Glyphosate induced an increase in malondialdehyde in Z. tuberculosa leaves. The lowest values of chlorophyll a content 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 Glyphosate is phytotoxic to Z. tuberculosa by promoting biochemical, anatomical and morphological alterations. The morphoanatomical injuries found on Z. tuberculosa are severe, suggesting that the presence of glyphosate can impact this species irreversibly and compromise its survival.

Simulated derive of glyphosate in green onion plants (Allium fistulosum L.)

The effect of simulated glyphosate drift on common chives (Allium fistulosum L.) was evaluated. The work was developed in a private garden, in Confresa-MT, from January to February 2016. The experiment consists of 6 treatments with 4 repetitions, arranged in a completely randomized design (DIC). The treatments were formed b 6 sub doses of glyphosate: 0,54,108,162,216 and 270 g.i.a ha-1 . At 7 and 14 days after application of the sub doses of the herbicide glyphosate, the plants were subjected to visual analysis of phytointoxication, using notes, on a scale ranging from 0 to 10. At 14 days after application of herbicide, the number total leaves, number of dead leaves, number of tillers, fresh weight of commercial leaf and root length.

Biological response of maize hybrids to simulated glyphosate drift

The effect of simulated glyphosate drift on six maize hybrids (NS 6102, as 334, Lucius, Confites, DKC 5031 and P0216) was investigated in Kulpin during the vegetation season of 2018. Glyphosate was applied in two growth stages: in stages 3-4 and 6-7 of fully formed maize leaves, with five different sublethal doses of the herbicide: 10, 20, 40, 80, 160 g ha-1. Phytotoxicity assessments of glyphosate were performed 7, 14, and 21 days after herbicide application. Analysis of the results has shown that glyphosate in the dose of 160 g ha-1 in the phase of 3-4 maize leaves caused only slight damages, without affecting the height and grain yield, while phytotoxicity was not observed at lower applied doses. Significant phytotoxicity on maize plants in the form of chlorosis, leaf curling and notable necrotic area was found when applying glyphosate in the dose of 160 g ha-1 in the phase of 6-7 leaves. Maize hybrids tested in this treatment have achieved an 81% lower yield on average, when compared to the control. Hybrids treated with the dose of 80 g ha-1 of glyphosate had a reduced yield by 30%, while in other lower doses the reduction in yield ranged between 25 and 18%, compared to the control.

Drift Distance in Aircraft Glyphosate Application Using Rice Plants as Indicators

ABSTRACT: This study aimed to evaluate the potential for glyphosate drift during aerial application using rice plants as sentinels, aiming to determine the effect of drift on irrigated rice crops. For this purpose, a field experiment was performed using an entirely randomized design with four replicates, evaluating different distances from the site of application [control (no application), 0, 12.5, 25, 50, 75, 100, 150, 200, 300, and 400 m]. The experiment was carried out at the Granjas 4 Irmãos farm, located in the Rio Grande city, Rio Grande do Sul State, Brazil. The glyphosate dose application was 1,920 g e.a. ha-1 (Roundup Transorb®, 480 g e.a. L-1 glyphosate isopropylamine salt). A dose-response curve was developed to estimate the drift rate in sentinel plants, by applying increasing glyphosate doses in rice plants and assessing the injury level. The drift rates estimated by the injury level in sentinel plants were 14% (150 m), 13% (200 m), and 5% (400 m). Death of the experimental units was observed for distances between 0 and 50 m, while in distances between 75 and 150 m, 25 to 50% of the plants survived, reducing productivity. In the distances between 200 and 400 m, there was no reduction in productivity when compared to the control, even when the injury levels reached 52 to 82%. Thus, we concluded that a 5% glyphosate drift reached up to 400 m from the application range. Considering the recommendation of zero drift, distances greater than 400 m should be adopted to avoid symptoms in rice plants. We suggest using distances of more than 400 m in future studies.

INTERAÇÕES ENTRE ADJUVANTE E PONTAS HIDRÁULICAS NO CONTROLE DA DERIVA DE GLIFOSATO

Interações entre adjuvante e pontas hidráulicas no controle da deriva de glifosato LUCAS CAIXETA VIEIRA1, JOÃO DE DEUS GODINHO JUNIOR2, RENATO ADRIANE ALVES RUAS3, VINÍCIUS RIBEIRO FARIA4, ALBERTO CARVALHO FILHO5 1 Departamento de Produção Vegetal, Universidade de São Paulo, Av. Pádua Dias, N0: 11, Agronomia, CEP: 13418-900, Piracicaba – São Paulo, Brasil, [email protected] 2 Departamento de Engenharia Rural, Universidade Estadual Paulista, Via de Acesso Professor Paulo Donato Castelane Castellane S/N - Vila Industrial, CEP: 14884-900, Jaboticabal – São Paulo, Brasil, [email protected] 3 Instituto de Ciências Agrárias, Universidade Federal de Viçosa, Rodovia MG-230 - Km 7, Zona Rural, CEP: 38810-000, Rio Paranaíba – Minas Gerais, Brasil, [email protected] 4 Instituto de Ciências Agrárias, Universidade Federal de Viçosa, Rodovia MG-230 - Km 7, Zona Rural, CEP: 38810-000, Rio Paranaíba – Minas Gerais, Brasil, [email protected] 5 Instituto de Ciências Agrárias, Universidade Federal de Viçosa, Rodovia MG-230 - Km 7, Zona Rural, CEP: 38810-000, Rio Paranaíba – Minas Gerais, Brasil, [email protected] RESUMO: Objetivou-se com este trabalho analisar as interações entre adjuvante e pontas hidráulicas no controle da deriva de glifosato. Primeiramente, avaliou-se o espectro de gotas, empregando-se o delineamento inteiramente casualizado (DIC), em parcela subdividida, avaliando-se quatro soluções de aplicação (Parcelas): água; água + óleo mineral; água + glifosato; água + óleo mineral + glifosato e três modelos de pontas tipo leque(Subparcelas): simples (SL); duplo (DL) e duplo com indução de ar (DLI), com seis repetições. Determinou-se o diâmetro da mediana volumétrica; densidade de gotas; amplitude relativa e o potencial risco de deriva. Na etapa seguinte à deriva foi quantificada em túnel de vento, empregando o DIC em parcela sub subdividida, sendo avaliadas as quatro soluções de aplicação (Parcelas), os três modelos de pontas (Subparcelas), em duas velocidades de vento (Sub subparcelas): 1,0 e 2,0 m s-1, com quatro repetições. Independentemente da solução de aplicação, a ponta DL apresentou os maiores valores de deriva, seguida da SL e DLI, respectivamente. A solução de aplicação água + óleo mineral + glifosato, proporcionou os menores valores de deriva para todas pontas hidráulicas avaliadas. A interação do glifosato com o óleo mineral, aplicado com a ponta DLI, tem potencial para reduzir a deriva no campo. Palavras-chave: tecnologia de aplicação, túnel de vento, espectro de gotas, redução de perdas, controle de qualidade. Interactions between adjuvant and hydraulic nozzles in the control of glyphosate drift ABSTRACT: The aim of this work was to analyze the interactions between adjuvant and the hydraulic nozzle in glyphosate drift control. Firstly, the droplet spectrum was evaluated using a completely randomized design (DIC) in a split plot, evaluating four application solutions (plots): water; water + mineral oil; water + glyphosate; water + mineral oil + glyphosate and three nozzle spray models (subplots): simple (SL); double (DL) and double with air induction (DLI), with six repetitions. The diameter of the volumetric median was determined; droplet density; relative amplitude and the potential risk of drift. In the following stage the drift was quantified in a wind tunnel, using the sub-subdivided DIC, being evaluated the four application solutions (parcels), the three nozzle spray models (subplots), in two wind speeds (sub-plots): 1.0 and 2.0 m s-1, with four repetitions. Regardless of the application solution, the DL tip presented the highest drift values, followed by SL and DLI, respectively. The application solution water + mineral oil + glyphosate, provided the lowest drift values ​​for all hydraulic tips evaluated. The interaction of glyphosate with mineral oil, applied with the DLI tip, has the potential to reduce drift in the field. Keywords: application technology, wind tunnel, spectrum of drops, loss reduction, quality control.

Sensitivity and Recovery of Grain Sorghum to Simulated Drift Rates of Glyphosate, Glufosinate, and Paraquat

A field experiment was conducted in 2017 and 2018 to evaluate the sensitivity and recovery of grain sorghum to the simulated drift of glufosinate, glyphosate, and paraquat at two application timings (V6 and flag leaf growth stage). Paraquat drift caused maximum injury to sorghum plants in both years, whereas the lowest injury was caused by glyphosate in 2017. Averaged over all herbicide treatments, injury to grain sorghum from the simulated herbicide drift was 5% greater when herbicides were applied at flag leaf stage, as compared to herbicide applications at the six-leaf stage in 2017. In 2018, injury from glyphosate drift was higher when applied at the six-leaf stage than at the flag leaf stage. Paraquat and glufosinate drift caused more injury when applied at flag leaf stage than at six-leaf stage at 14 days after application in 2018. About 21% to 29% of injury from the simulated drift of paraquat led to a 31% reduction in grain sorghum yield, as compared to a nontreated check in 2017. The simulated drift of glyphosate and glufosinate did not result in any significant yield reduction compared to the nontreated check in 2017, possibly due to the recovery of sorghum plants after herbicides’ drift application.