Efeitos de doses subletais de glyphosate no crescimento, consumo de água e absorção de nutrientes em Urochloa decumbens
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Data
2019-11-08
Autores
Moraes, Carolina Pucci de [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
A espécie Urochloa decumbens é uma das plantas mais importantes e frequentes em áreas com culturas perenes e em áreas não-agrícolas. Os efeitos secundários que ocorrem nas plantas pela aplicação de baixas doses de glyphosate ainda são pouco compreendidos. Desse modo, a hipótese dessa pesquisa foi de que as baixas doses de glyphosate podem suprimir o crescimento, reduzir a competição e permitir a sua utilização para manutenção da cobertura vegetal. Assim, o objetivo do trabalho foi avaliar os efeitos de doses subletais de glyphosate no crescimento, consumo de água, metabolismo e absorção de nutrientes em plantas de U. decumbens. Foram realizados três experimentos em casa de vegetação, seguindo delineamento em blocos casualizados, com três doses de glyphosate (0; 22,5 e 45 g e.a. ha-1) e cinco repetições. As unidades experimentais utilizadas nos experimentos foram constituídas por duas estruturas plásticas acopladas, sendo a superior preenchida com 500 g de substrato comercial e semeada com U. decumbens, e a inferior com 650 mL de água. Aos 15 dias após a semeadura (DAS) realizou-se o desbaste, mantendo 20 plantas por unidade e aos 16 DAS a aplicação dos tratamentos utilizando pulverizador estacionário. Na primeira avaliação, de consumo de água, os três experimentos corresponderam aos períodos de avaliação em dias após aplicação (DAA), sendo feitas medições do volume de água remanescente na estrutura inferior a cada 48 horas, com reposição do volume inicial de 0-15 DAA; 0-30 DAA e rebrota das plantas (16-30 DAA). Ao término de cada experimento, procedeu-se a contagem dos perfilhos e coleta da parte aérea das plantas para a determinação de massa seca. Na sequência, calculou-se o coeficiente de transpiração aos 15 e 30 DAA. Na segunda avaliação, foram quantificados os teores de fenilalanina, tirosina, triptofano e dos ácidos chiquímico e quínico por cromatografia líquida e espectrometria de massas (LC-MS/MS). Na última avaliação, foram determinados os teores dos macronutrientes nas plantas. A aplicação de baixas doses de glyphosate reduziu o consumo de água acumulado, acúmulo de macronutrientes e a biomassa de plantas de U. decumbens, porém os efeitos observados foram mais intensos e mais persistentes na dose de 45 g e.a. ha-1. A aplicação da maior dose de glyphosate promoveu aumento do perfilhamento nas plantas. Os resultados de consumo de água, acúmulos de massa seca e de macronutrientes encontrados nos experimentos, demonstraram a efetividade da dose de 45 g e.a. ha-1, indicando potencial uso para redução do crescimento ou manutenção da cobertura vegetal de plantas de U. decumbens. As baixas doses de glyphosate interferiram no metabolismo das plantas, com redução no acúmulo dos aminoácidos aromáticos e ácidos fenólicos nos períodos avaliados, com exceção da rebrota. A aplicação de baixas doses de glyphosate resultou em menor absorção de macronutrientes pelas plantas, com exceção do enxofre, até 15 DAA e durante a rebrota.
The species Urochloa decumbens is one of the most important and frequent plants in perennial and non-agricultural areas. The secondary effects that occur on plants by the application of low doses of glyphosate, are still poorly understood. Thus, the hypothesis of this research was that low doses of glyphosate may suppress growth, reduce competition and allow the use for maintenance of vegetation cover. Therefore, the objective of this study was to evaluate the effects of sublethal doses of glyphosate on the growth, water consumption, metabolism and nutrient absorption on U. decumbens plants. Three greenhouse experiments were carried out, following a randomized block design with three doses of glyphosate (0, 22.5 and 45 g a.e. ha-1) and five replications. The experimental units used in the experiments consisted of two coupled plastic structures, the upper one filled with 500 g of commercial substrate and sowed with U. decumbens, and the lower with 650 mL of water. At 15 days after sowing (DAS) plants were thinned, maintaining 20 plants per unit and at 16 DAS the application of treatments using a stationary sprayer. In the first evaluation, of water consumption, the three experiments corresponded to the evaluation periods in days after application (DAA), with measurements of the remaining water volume in the lower structure every 48 hours, with initial volume replacement from 0-15 DAA; 0-30 DAA and regrowth of plants (16-30 DAA). At the end of each experiment, the tillers were counted and the shoot plants was collected to determine the dry mass. Subsequently, the transpiration coefficient was calculated at 15 and 30 DAA. In the second evaluation, the contents of phenylalanine, tyrosine, tryptophan and shikimic and quinic acids were quantified liquid chromatography and mass spectrometry (LC-MS/MS). In the last evaluation, the macronutrients contents of plants were determined. The application of low doses of glyphosate reduced the accumulated water consumption, macronutrient accumulation and plant biomass of U. decumbens, but the observed effects were more intense and more persistent at the dose of 45 g a.e. ha-1. The application of the highest dose of glyphosate increased plant tillering. The results of water consumption, dry matter accumulation and macronutrients found in the experiments demonstrated the effectiveness of the dose of 45 g a.e. ha-1, indicating potential use for growth reduction or maintenance of the vegetation cover of U. decumbens plants. The low doses of glyphosate interfered in plant metabolism, with reduction in the accumulation of aromatic amino acids and phenolic acids in the evaluated periods, except for regrowth. The application of low doses of glyphosate resulted in lower macronutrient absorption by plants, except for sulfur, up to 15 DAA and during regrowth.
The species Urochloa decumbens is one of the most important and frequent plants in perennial and non-agricultural areas. The secondary effects that occur on plants by the application of low doses of glyphosate, are still poorly understood. Thus, the hypothesis of this research was that low doses of glyphosate may suppress growth, reduce competition and allow the use for maintenance of vegetation cover. Therefore, the objective of this study was to evaluate the effects of sublethal doses of glyphosate on the growth, water consumption, metabolism and nutrient absorption on U. decumbens plants. Three greenhouse experiments were carried out, following a randomized block design with three doses of glyphosate (0, 22.5 and 45 g a.e. ha-1) and five replications. The experimental units used in the experiments consisted of two coupled plastic structures, the upper one filled with 500 g of commercial substrate and sowed with U. decumbens, and the lower with 650 mL of water. At 15 days after sowing (DAS) plants were thinned, maintaining 20 plants per unit and at 16 DAS the application of treatments using a stationary sprayer. In the first evaluation, of water consumption, the three experiments corresponded to the evaluation periods in days after application (DAA), with measurements of the remaining water volume in the lower structure every 48 hours, with initial volume replacement from 0-15 DAA; 0-30 DAA and regrowth of plants (16-30 DAA). At the end of each experiment, the tillers were counted and the shoot plants was collected to determine the dry mass. Subsequently, the transpiration coefficient was calculated at 15 and 30 DAA. In the second evaluation, the contents of phenylalanine, tyrosine, tryptophan and shikimic and quinic acids were quantified liquid chromatography and mass spectrometry (LC-MS/MS). In the last evaluation, the macronutrients contents of plants were determined. The application of low doses of glyphosate reduced the accumulated water consumption, macronutrient accumulation and plant biomass of U. decumbens, but the observed effects were more intense and more persistent at the dose of 45 g a.e. ha-1. The application of the highest dose of glyphosate increased plant tillering. The results of water consumption, dry matter accumulation and macronutrients found in the experiments demonstrated the effectiveness of the dose of 45 g a.e. ha-1, indicating potential use for growth reduction or maintenance of the vegetation cover of U. decumbens plants. The low doses of glyphosate interfered in plant metabolism, with reduction in the accumulation of aromatic amino acids and phenolic acids in the evaluated periods, except for regrowth. The application of low doses of glyphosate resulted in lower macronutrient absorption by plants, except for sulfur, up to 15 DAA and during regrowth.
Descrição
Palavras-chave
Aminoácidos aromáticos, Capim-braquiária, Herbicida, Metabolismo, Nutrição mineral, Regulador de crescimento, Aromatic amino acids, Signalgrass, Herbicide, Metabolism, Mineral nutrition, Growth regulator