Crescimento, desenvolvimento e produtividade de arroz submetido a baixas doses de glyphosate
Data
2018-05-18
Autores
Macedo, Gabrielle de Castro [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
O emprego de substâncias tóxicas as plantas, como o glyphosate, em doses muito menores que as recomendadas comercialmente pode ocasionar alterações em varáveis como crescimento, acúmulo de biomassa, altura, conteúdo de proteína e resistência a doenças. Desta forma, os objetivos deste trabalho foram realizar estudos para uma melhor compreensão das alterações bioquímicas, fisiológicas e fenológicas do arroz causadas por subdoses de glyphosate. O experimento 1 foi realizado à campo, na Fazenda Experimental Lageado, pertencente à Faculdade de Ciências Agronômicas, FCA/UNESP, Botucatu/SP, nos anos agrícolas de 2015/2016 e 2016/2017. O delineamento experimental utilizado foi o de blocos casualizados, arranjado em esquema fatorial 2x7, sendo o primeiro fator época de aplicação do glyphosate (V3 ou R1) e, o segundo, as doses do herbicida (0; 7,5; 15; 30; 60; 120 e 240 g e.a. ha-1), com quatro repetições. Foram avaliados a produtividade, o comprimento de panículas, número de perfilhos por m², peso de 1000 grãos, número de grãos por panícula, a fertilidade de espiguetas e o número de dias entre a aplicação e o início de cada fase fenológica. Os experimentos 2 e 3 foram realizados em casa de vegetação, no Núcleo de Pesquisas Avançadas em Matologia (NUPAM), pertecentente à Faculdade de Ciências Agronômicas, FCA/UNESP, Botucatu/SP. O experimento 2 seguiu delineamento inteiramente casualizado em esquema fatorial (7x3) com cinco repetições. Os tratamentos foram constituídos por sete doses do herbicida glyphosate (0; 7,5; 15; 30; 60; 120 e 240 g e.a. ha-1) aplicados no estádio V3, e 3 períodos de chuva após a aplicação (12, 24 horas e ausência). Foram avaliados o perfilhamento e o acúmulo de massa das plantas. O experimento 3 foi arranjado em delineamento inteiramente casualizado em esquema fatorial (7x3) com quatro repetições. Os tratamentos foram constituídos por dez doses do herbicida glyphosate (0; 1,5; 3; 6; 12; 24; 36; 72; 180 e 360 g e.a. ha-1), aplicadas quando as plantas se encontravam em estádio V4, e três regimes de fornecimento de água (fornecimento contínuo, RH1 e RH2). Foram avaliados o consumo de água diário, o perfilhamento e o acúmulo de massa das plantas. A aplicação de subdoses de glyphosate em condições de campo não influenciou a produtividade e os componentes de produtividade das plantas de arroz até a dose de 60 g e.a. ha-1 de glyphosate quando a aplicação ocorreu em V3, e até 30 g e.a. ha-1 de glyphosate quando a aplicação ocorreu em R1. A partir destas doses, houve severo efeito de intoxicação da cultura. Observou-se que os diferentes períodos de chuva após a aplicação de subdoses de glyphosate não interferiram na resposta das plantas de arroz aos tratamentos. Não foi observado efeito hormético para acúmulo de biomassa e consumo de água em casa de vegetação. A aplicação de doses entre 30 e 240 g e.a. ha-1 de glyphosate proporcionou incremento do perfilhamento das plantas de arroz em todos os estudos realizados, sendo a dose que causou incremento dependente das condições de condução do estudo.
The use of toxic substances in plants, such as glyphosate, in doses much smaller than those recommended commercially can cause changes in variables such as growth, biomass accumulation, height, protein content and resistance to diseases. In this way, the objectives of this work were to carry out studies for a better understanding of the biochemical, physiological and phenological alterations of the paddy rice caused by glyphosate subdoses. Experiment 1 was carried out at the Experimental Farm Lageado, belonging to the College of Agronomic Sciences, FCA / UNESP, in Botucatu, Sao Paulo, in the agricultural years of 2015/2016 and 2016/2017. The experimental design was a randomized block arranged in a 2x7 factorial scheme, with the first factor being the glyphosate application time (V3 or R1) and the second herbicide dose (0, 7.5, 15, 30, 60, 120 and 240 g a.e. ha-1), with four replications. The productivity, panicle length, number of tillers per m², weight of 1000 grains, number of grains per panicle, spikelet fertility and the number of days between the application and the beginning of each phenological phase were evaluated. Experiments 2 and 3 were carried out in a greenhouse at the Weed Science Advanced Research Center (NUPAM), belonging to the Faculty of Agronomic Sciences, FCA / UNESP, in Botucatu, Sao Paulo. Experiment 2 was in a completely randomized design in a factorial scheme (7x3) with five replications. The factor one was doses of the herbicide glyphosate (0, 7.5, 15, 30, 60, 120 and 240 g a.e. ha-1) applied in the V3 and factor two was rainy periods after application (12, 24 hours and without rain). The tillering and mass accumulation of plants were evaluated. Experiment 3 was arranged in a completely randomized design in a factorial scheme (7x3) with four replications. The factor one consisted of ten doses of the herbicide glyphosate (0, 1.5, 3, 6, 12, 24, 36, 72, 180 and 360 g a.e. ha-1) applied when plants were in the V4 stage, and factor two was 3 water supply schemes (no stress, RH1 and RH2). Daily water consumption, tillering and plant mass accumulation were evaluated. The application of glyphosate subdoses under field conditions did not influence yield, productivity components or phenology of paddy rice plants up to the 60 g a.e. ha-1 of glyphosate when the application occurred in V3 and up to 30 g a.e. ha-1 of glyphosate when application occurred at R1. From these doses, there was a severe effect of intoxication of the culture. It was observed that different rainy periods after application of glyphosate subdoses did not interfere in the response of paddy rice plants to the treatments. At greenhouse conditions, no hormesis effect was observed for biomass accumulation and water consumption. The application of doses from 30 to 240 g a.e. ha-1 of glyphosate increased the tillering of paddy rice plants in all the studies carried out, being the dose that caused increment dependent of the conditions of conduction of each study.
The use of toxic substances in plants, such as glyphosate, in doses much smaller than those recommended commercially can cause changes in variables such as growth, biomass accumulation, height, protein content and resistance to diseases. In this way, the objectives of this work were to carry out studies for a better understanding of the biochemical, physiological and phenological alterations of the paddy rice caused by glyphosate subdoses. Experiment 1 was carried out at the Experimental Farm Lageado, belonging to the College of Agronomic Sciences, FCA / UNESP, in Botucatu, Sao Paulo, in the agricultural years of 2015/2016 and 2016/2017. The experimental design was a randomized block arranged in a 2x7 factorial scheme, with the first factor being the glyphosate application time (V3 or R1) and the second herbicide dose (0, 7.5, 15, 30, 60, 120 and 240 g a.e. ha-1), with four replications. The productivity, panicle length, number of tillers per m², weight of 1000 grains, number of grains per panicle, spikelet fertility and the number of days between the application and the beginning of each phenological phase were evaluated. Experiments 2 and 3 were carried out in a greenhouse at the Weed Science Advanced Research Center (NUPAM), belonging to the Faculty of Agronomic Sciences, FCA / UNESP, in Botucatu, Sao Paulo. Experiment 2 was in a completely randomized design in a factorial scheme (7x3) with five replications. The factor one was doses of the herbicide glyphosate (0, 7.5, 15, 30, 60, 120 and 240 g a.e. ha-1) applied in the V3 and factor two was rainy periods after application (12, 24 hours and without rain). The tillering and mass accumulation of plants were evaluated. Experiment 3 was arranged in a completely randomized design in a factorial scheme (7x3) with four replications. The factor one consisted of ten doses of the herbicide glyphosate (0, 1.5, 3, 6, 12, 24, 36, 72, 180 and 360 g a.e. ha-1) applied when plants were in the V4 stage, and factor two was 3 water supply schemes (no stress, RH1 and RH2). Daily water consumption, tillering and plant mass accumulation were evaluated. The application of glyphosate subdoses under field conditions did not influence yield, productivity components or phenology of paddy rice plants up to the 60 g a.e. ha-1 of glyphosate when the application occurred in V3 and up to 30 g a.e. ha-1 of glyphosate when application occurred at R1. From these doses, there was a severe effect of intoxication of the culture. It was observed that different rainy periods after application of glyphosate subdoses did not interfere in the response of paddy rice plants to the treatments. At greenhouse conditions, no hormesis effect was observed for biomass accumulation and water consumption. The application of doses from 30 to 240 g a.e. ha-1 of glyphosate increased the tillering of paddy rice plants in all the studies carried out, being the dose that caused increment dependent of the conditions of conduction of each study.
Descrição
Palavras-chave
Hormesis, EPSPs, Oryza sativa L., subdoses, efeitos secundários de herbicidas