Relação entre o consumo de água e a absorção de herbicidas em plantas daninhas e cana-de-açúcar

O objetivo deste trabalho foi avaliar a relação entre o consumo de água pelas plantas de cana-de-açúcar e plantas daninhas e a absorção de herbicidas. O trabalho foi desenvolvido em dois experimentos: no primeiro, mediu-se o consumo de água através da pesagem diária das espécies de plantas daninhas Digitaria horizontalis, Panicum maximum, Ipomoea grandifolia, Ipomoea hederifolia, Brachiaria decumbens, assim como para os cultivares de cana-deaçúcar PO8862, SP80 3280 e RB83 5486; e, no segundo, foram determinadas as concentrações do amicarbazone, imazapic, tebuthiuron e hexazinone no xilema dos três cultivares de cana-deaçúcar e de I. grandifolia por meio da bomba de Schollander e de cromatografia e espectrometria de massas (LC-MS). A taxa de transpiração e, consequentemente, a taxa de consumo de água mostraram-se determinantes da taxa de absorção de herbicidas pelas plantas de diferentes espécies de plantas daninhas e cultivares de cana-de-açúcar. As concentrações de herbicidas na seiva do xilema foram variáveis em função da espécie e do herbicida em contato com o sistema radicular, indicando que a facilidade de absorção pelas raízes pode ser determinante para eficácia e/ou seletividade de herbicidas.The objective of this work was to evaluate the relationship between water consumption by sugarcane plants and weeds and herbicide absorption. Two experiments were carried out. In the first, water consumption was measured by daily weighing the weed species Digitaria horizontalis, Panicum maximum, Ipomoea grandifolia, Ipomoea hederifolia, Brachiaria decumbens, as well as the sugarcane cultivars PO8862, SP80 3280, and RB83 5486. In the second experiment, the concentrations of amicarbazone, imazapic, tebuthiuron and hexazinone in the xylem of the three sugarcane cultivars and I. grandifolia were measured using the Schollander pump and chromatography and mass spectrometry (LC MS). The transpiration rate and, consequently, the water consumption rate were determinants of the rate of herbicide absorption by the different weed species and sugarcane cultivars. The herbicide concentrations in the xylem sap varied according to the species and herbicide in contact with the root system, indicating that easy absorption by the roots can be crucial to the effectiveness and/or selectivity of herbicides

Avaliação da intoxicação de cultivares de cana-de-açúcar e I. grandifolia ao amicarbazone

O objetivo deste trabalho foi avaliar a intoxicação de planta daninha e cultivares de cana-de-açúcar ao amicarbazone. Para isso, utilizou-se Ipomoea grandifolia como planta daninha representante e os cultivares de cana-de-açúcar PO8862, SP80 3280 e RB83 5486, caracterizados como sensível, intermediário e tolerante aos herbicidas, respectivamente. Foi verificado o consumo de água e quantificada a concentração do amicarbazone em seiva de xilema dos três cultivares de cana-de-açúcar e de I. grandifolia por meio da bomba de Schollander e da cromatografia e espectrometria de massas (LC-MS). A intoxicação das plantas foi verificada através de leituras da fluorescência, com auxílio do fluorômetro portátil, que permitiu a correlação da taxa de transporte de elétrons (ETR) com a concentração de amicarbazone absorvido pelos cultivares de cana-de-açúcar e por I. grandifolia. Verificou-se, através do experimento, que a redução dos valores da ETR pode ser utilizada para indicar o nível de intoxicação de I. grandifolia e de plantas de cana-de-açúcar ao amicarbazone. I. grandifolia destacou-se em relação à cana-de-açúcar pela maior sensibilidade ao amicarbazone. A suscetibilidade diferencial dos cultivares de cana-de-açúcar PO8862, SP80 3280 e RB83 5486 pode ser justificada, possivelmente, pela absorção diferencial do amicarbazone entre os cultivares.The objective of this work was to evaluate the intoxication of weeds and sugarcane cultivars by amicarbazone. Ipomoea grandifolia was used as weed representative and the sugarcane cultivars PO8862, SP80 3280, and RB835486, characterized as sensitive, intermediate and tolerant to herbicides, respectively. Water consumption was verified and amicarbazone concentration quantified in the xylem sap of the three sugarcane cultivars and of I. grandifolia, using the Schollander pump and chromatography and mass spectrometry (LC-MS). Plant intoxication was verified by fluorescence readings with the aid of portable fluorometer, which allowed the correlation of the electron transport rate (ETR) with the concentration of amicarbazone absorbed by the sugarcane cultivars and I. grandifolia. Thus, it could be verified through experiments that the reduction of ETR values may be used to indicate the level of intoxication of I. grandifolia, and sugarcane plants by amicarbazone. I. grandifolia was more sensitive to amicarbazone than sugarcane. The differential susceptibility of the sugarcane varieties PO8862, SP80 3280, and RB83 5486 can be justified possibly by the differential absorption of amicarbazone among cultivars

Efeitos na taxa de transporte de elétrons de plantas daninhas após aplicação de amicarbazone

Entre os herbicidas registrados para cana-de-açúcar, o amicarbazone é um dos mais importantes para o controle das plantas daninhas, sendo preciso que o herbicida seja absorvido, translocado e que ele alcance os cloroplastos das células das folhas para atuar em seu sítio de ligação no fotossistema II. O objetivo deste trabalho foi avaliar os efeitos da aplicação do amicarbazone na taxa de transporte de elétrons (ETR) de Ipomoea grandifolia, Brachiaria decumbens e Digitaria horizontalis. Foi verificada a resposta dessas plantas daninhas, em relação à ETR, quando submetidas ao amicarbazone em solução e na sequência à solução sem herbicida, por meio de leituras da ETR, realizadas em folhas novas e adultas com o uso de um fluorômetro portátil. Verificou-se também o consumo de água das plantas daninhas pela pesagem diária dos recipientes contendo a solução e as plantas. Assim, verificou-se por meio do experimento que a redução dos valores da ETR pode ser utilizada para indicar o nível de intoxicação nas plantas daninhas em estudo. As plantas daninhas I. grandifolia, B. decumbens e D. horizontalis apresentaram respostas diferenciadas quando submetidas a solução sem herbicida após solução com amicarbazone. I. grandifolia apresentou-se mais sensível ao amicarbazone devido à maior dificuldade em recuperar os níveis iniciais de ETR, além de apresentar alterações nas folhas novas após o termino de fornecimento do herbicida. O consumo de água pode explicar esse comportamento em I. grandifolia, visto tratar-se da espécie que mais consumiu água e, consequentemente, mais absorveu o amicarbazone. Já para B. decumbens e D. horizontalis ocorreram menores níveis de absorção de água e, por conseguinte, as folhas velhas tiveram melhor recuperação do transporte de elétrons e não houve intoxicação em folhas novas.Amicarbazone is one of the most important herbicides registered for weed control in sugarcane. It must be absorbed, translocated, and reach the chloroplasts of leaf cells to act on its binding site in the photosystem II. The objective of this work was to evaluate the effects of applying amicarbazone on the electron ltransport rate (ETR) of Ipomoea grandifolia, Brachiaria decumbens and Digitaria horizontalis. The response of these weeds to ETR, was verified when submitted to amicarbazone in solution and in sequence to the solution without herbicide, by ETR readings on adult and young leaves, using a portable fluorometer. Water consumption by the weeds was also verified by daily weighing of the containers with the solution and the plants. Thus, the experiment showed that the reduction of the ETR values may be used to indicate the level of intoxication in the weeds studied. The weeds I. grandifolia, B. decumbens and D. horizontalis showed different responses when exposed to herbicide-free solution after the solution with amicarbazone. I. grandifolia was more sensitive to amicarbazone due to the greater difficulty in recovering the initial ETR values, besides showing effects on young leaves after completion of the herbicide application.. Water intake can explain this behavior of I. grandifolia, since this species consumed the most water, thus absorbing amicarbazone the most. For B. decumbens and D. horizontalis, there was less water absorption, and, consequently, the old leaves had a better electron transport recovery, and the young leaves, no intoxication

Extraction and Simultaneous Determination of Glyphosate, AMPA and Compounds of the Shikimic Acid Pathway in Plants

This study has aimed to develop a method for simultaneous extraction and determination by liquid chromatography and mass spectrometry (LC-MS/MS) of glyphosate, aminomethylphosphonic acid (AMPA), shikimic acid, quinic acid, phenylalanine, tyrosine and tryptophan. For the joint analysis of these compounds the best conditions of ionization in mass spectrometry and for chromatographic separation of the compounds were selected. Calibration curves and linearity ranges were also determined for each compound. Different extraction systems of the compounds were tested from plant tissues collected from sugarcane (Saccharum officinarum) and eucalyptus (Eucalyptus urophylla platiphylla) plants two days after the glyphosate application at the dose of 720 g a.e. ha-1. The plant material was dried in a forced air circulation drying oven and in a lyophilizer, and subsequently the extractions with acidified water (pH 2.5), acetonitrile-water (50:50) [v/v] and methanol-water (50:50) [v/v] were tested. To verify the recovery of the compounds in the plant matrix with acidified water as an extracting solution, the samples were fortified with a solution containing the mixture of the different analytical standards present so that this one presented the same levels of 50 and 100 μg L-1 of each compound. All experiments were conducted with three replicates. The analytical method developed was efficient for compounds quantifications. The extraction from the samples dried in an oven and using acidified water allowed better extraction levels for all compounds. The recovery levels of the compounds in the fortified samples with known amounts of each compound for both plants samples were rather satisfactory

Dynamics of Clomazone Formulations Under Different Applications Conditions

ABSTRACT: Maintenance of straw on the soil surface in sugarcane production areas can influence weed occurrence and herbicide dynamics. After application, considerable losses of clomazone can occur as a result of its physicochemical characteristics. For this reason, novel formulations have been developed. In addition to the conventional formulation, microencapsulated formulations are currently available. Thus, the aim of this study was to observe and compare the effect of clomazone formulations under different application conditions. For this purpose, the experiment was carried with 12 treatments in a completely randomized design, with four replications, using clomazone formulations (1,200 g a.i. ha-1), on soils with different moisture levels, in the presence and absence of sugarcane straw, followed or not by rainfall simulation. The treatments were compared by observation of number of emerged plants and phytotoxicity at 7 and 14 DAA, as well shoot dry matter at 14 DAA for Ipomoea nil, Urochloa decumbens and Panicum maximum. In general, the microencapsulated formulation presented a better performance under the less suitable application conditions when compared to the conventional one. However, for the other conditions, both formulations had a similar performance.</jats:p