Glyphosate translocation in herbicide tolerant plants

The objective of this study was to evaluate glyphosate translocation in glyphosate-tolerant weed species (I. nil, T. procumbens and S. latifolia) compared to glyphosate-susceptible species (B. pilosa). The evaluations of 14C-glyphosate absorption and translocation were performed at 6, 12, 36 and 72 hours after treatment (HAT) in I. nil and B. pilosa, and only at 72 HAT in the species T. procumbens and S. latifolia. The plants were collected and fractionated into application leaf, other leaves, stems, and roots. In S. latifolia, approximately 88% of the glyphosate remained in the application leaf and a small amount was translocated to roots at 72 HAT. However, 75% of the herbicide applied on T. procumbens remained in the leaf that had received the treatment, with greater glyphosate translocation to the floral bud. It was concluded that the smaller amount of glyphosate observed in S. latifolia and T. procumbens may partly account for their higher tolerance to glyphosate. However, I. nil tolerance to glyphosate may be associated with other factors such as metabolization, root exudation or compartmentalization, because a large amount of the herbicide reached the roots of this species.Objetivou-se neste estudo avaliar a translocação de glyphosate em plantas tolerantes (Ipomoea nil, Tridax procumbens e Spermacoce latifolia) e suscetível (Bidens pilosa) a esse herbicida. As avaliações de absorção e translocação do 14C-glyphosate em I. nil e B. pilosa foram efetuadas às 6, 12, 36 e 72 horas após a aplicação do herbicida (HAT), e em T. procumbens e S. latifolia, às 72 HAT. As plantas foram coletadas e fracionadas em: folha de aplicação, demais folhas, caules e raízes; em T. procumbens e S. latifolia, avaliou-se a presença do produto na inflorescência da planta. Em S. latifolia, aproximadamente 88% do glyphosate permaneceu na folha de aplicação, e pequena quantidade translocou para as raízes. Todavia, em T. procumbens, 75% do herbicida permaneceu na folha que recebeu a aplicação, observando-se maior translocação na inflorescência em relação às raízes. Conclui-se que a menor translocação do glyphosate observada em S. latifolia e T. procumbens pode ser um dos fatores responsáveis pela maior tolerância dessas espécies ao herbicida, ao passo que em I. nil a metabolização, a exsudação radicular ou a compartimentalização podem favorecer a tolerância, já que grande quantidade do produto atingiu as raízes da espécie

Weed flora in rice areas under distinct cropping systems, herbicide and irrigation managements

We aimed to evaluate the incidence of weeds in the pre-planting of the summer crop as a function of planting system, herbicide use and irrigation management. The experiment was installed in field conditions, in RBD and 3 x 2 factorial scheme with eight replications. Treatments consisted in submitting rice to three management factors: water management – continuously flooded or intermittend irrigation (Factor A), coupled to the application (traditional control) or not (semi-ecological system) of herbicides (Factor B), and planting system – conventional soil tillage, minimum tillage and no till systems (Factor C). One year after rice cultivation, preceding the planting of the next cropping season, phytosociological evaluations of the weed communities were carried out. We assessed the overall infestation and weed species composition, which were classified by their respective density, frequency and dominance. We also estimated the diversity coefficients of Simpson and Shannon Weiner, and the sustainability coefficient of Shannon; treatments were also grouped by similarity in weed composition. In flood-irrigated rice, no till provides the lowest levels of weed infestation and, together with the conventional cropping system, results in values closer to the ecological sustainability; The application of herbicides in flooded rice crops reduces weed infestation, increases diversity and equalizes the ecological sustainability, compared to areas without the application of weed management methods. However, chemical control leads to the selection of resistant or tolerant species to herbicides, such as Polypogon sp.; Both continuous and intermittent water management systems did not cause changes in the level of infestation, composition or diversity coefficients

Práticas de manejo de solo em cultivos de sequeiro em terras baixas.

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Características micromorfológicas de biótipos de capim-arroz resistente e suscetível ao quinclorac.

RESUMO - O objetivo deste trabalho foi avaliar o efeito do quinclorac nas características anatômicas de folhas e raízes de biótipos de capim‑arroz (Echinochloa spp.), resistente e suscetível a este herbicida, por meio de avaliações micromorfométricas. As plantas foram cultivadas em vasos de plástico com capacidade de 250 cm3. As imagens dos cortes foram obtidas com microscópio de luz equipado com sistema U‑Photo, acoplado à câmera digital conectada a microcomputador. Na seção transversal da lâmina foliar e das raízes, utilizouse objetiva de 10X, tendo-se avaliado 20 cortes/campos por planta, com dez medições por corte e quatro repetições por tratamento. Observaram-se diferenças entre os biótipos resistente e suscetível, tanto na ausência quanto na presença do quinclorac. O biótipo resistente apresenta lâmina foliar pouco afetada pelo herbicida; no entanto, há modificação na constituição dos tecidos radiculares com a formação mais acentuada de aerênquima. O biótipo suscetível também apresenta formação de aerênquima quando tratado com o quinclorac, mas em quantidade inferior à observada no biótipo resistente. ABSTRACT- The objective of this work was to evaluate the effect of quinclorac on anatomical traits of leaves and roots of barnyardgrass (Echinochloa spp.) biotypes, susceptible and resistant to this herbicide, by micromorphometric assessments. Plants were grown in plastic pots with 250 cm3 capacity. The images of plant sections were obtained with a light microscope equipped with a U‑Photo system, coupled to a digital photo camera connected to a microcomputer. For cross-sections of leaf blades and roots, 10X objectives were used, and 20 sections/fields per plant were evaluated, with ten measurements per section and four replicates per treatment. Differences were observed between resistant and susceptible biotypes, both in the absence and in the presence of quinclorac. The resistant biotype shows leaf blades that are less affected by the herbicide; however, there are changes in root tissue constitution with increased aerenchyma formation. The susceptible biotype also shows formation of aerenchyma when treated with quinclorac, but in lower levels than those observed for the resistant biotype

Análise de viabilidade econômico-financeira da rotação arroz-soja, com o sistema sulco-camalhão, em terras baixas do Rio Grande do Sul.

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Caracterização de batata-doce de polpa roxa (ipomoea batatas (l.) lam.) em duas safras.

O objetivo desse trabalho foi a caracterização físico-química de um genótipo de batata-doce de polpa roxa (Ipomoea batatas (L.) Lam.) proveniente do banco de germoplasma da Embrapa Clima Temperado e produzido por um produtor local

Sweet Sorghum Establishment after Application of Residual Herbicides

Imazethapyr, sulfentrazone, clomazone, diclosulam, trifloxysulfuron-sodium and trifluralin are residual herbicides commonly used for weed control in soybean or sugarcane crops. The sorghum crop implanted succeeding sugarcane, can be affected by the carryover effect of these herbicides. In this context, we aim with this work to evaluate the minimum period between application of herbicides with residual effect (imazethapyr, sulfentrazone, clomazone, diclosulam, trifluralin and trifloxysulfuron-sodium) and the planting of sorghum so that there is no impairment in growth and establishment of this crop due to the herbicide carryover effect. The experiment was installed in randomized blocks design with four replications, under field conditions. The herbicides were applied to the previously tillaged soil, with sorghum being planted 0, 14, 28, 42, 56 and 70 days after herbicide application (DAA). The percentage of germination was evaluated daily from planting, and 7, 14, 21 and 28 days after emergence (DAE) of each planting, the phytotoxicity was evaluated. Thirty five DAE of each planting season, ten plants were collected per plot for measurement of leaf area, fresh and dry mass of plants, leaves and stems. The minimum time interval for planting sorghum after application of these herbicides varies, but imazethapyr is highlighted by causing high and durable toxicity to sorghum even when planting sorghum after 70 days of its application