Navegando por Autor "Santos, José Barbosa dos"

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Photosynthetic activity of coffee after application of glyphosate subdoses
(Editora da Universidade Estadual de Maringá - EDUEM, 2013-01) Carvalho, Felipe Paolinelli de; França, André Cabral; Lemos, Vinícius Teixeira; Ferreira, Evander Alves; Santos, José Barbosa dos; Silva, Antonio Alberto da
Farmers use non-selective herbicides, such as glyphosate, in directed applications to control weeds in coffee crops. Despite the precautions used during the application of herbicides, there are usually reports of poisoning in plantation areas. Moreover, it is fundamental to understand the effects of glyphosate on photosynthetic processes. The present study aimed to evaluate the characteristics associated with the photosynthetic activity in coffee cultivars subjected to doses of glyphosate. The experiment was conducted in a greenhouse using three varieties of coffee (Coffea arabica), including Acaiá (MG-6851), Catucaí Amarelo (2 SL) and Topázio (MG-1190), and three subdoses of glyphosate (0.0, 115.2 and 460.8 g ha -1 ) in a 3 x 3 factorial scheme. Herbicide application led to reduced internal carbon, ratio between internal and environmental carbon, carbon consumption and photosynthetic rate at 15 days after application (DAA) in the fourth leaf. In the same leaf at 45 DAA, the carbon consumption of the cultivars was even less. Despite low carbon concentrations, no difference in consumption and photosynthetic rate was observed in the last leaf. Glyphosate caused metabolic damage with transitory effects on the photosynthetic rate; the Acaiá cultivar was the most tolerant. These transitory effects may result in irreversible and prolonged damage to crop growth.
Water use efficiency by coffee arabica after glyphosate application
(Editora da Universidade Estadual de Maringá - EDUEM, 2014-07) Carvalho, Felipe Paolinelli de; França, André Cabral; Souza, Bruna Pereira de; Fialho, Cíntia Maria Teixeira; Santos, José Barbosa dos; Silva, Antonio Alberto da
Many coffee growers apply glyphosate in directed applications, but some phytotoxicity has been noted. It is believed some herbicides can exert a direct or indirect negative effect on photosynthesis by reducing the metabolic rate in a way that can affect the water use efficiency. The objective of this study was to investigate the variables related to water use among coffee cultivars subjected to the application of glyphosate and the effects of each dose. The experiment was conducted in a greenhouse using three varieties of coffee (Coffea arabica), Acaiá (MG-6851), Catucaí Amarelo (2SL) and Topázio (MG-1190), and three doses of glyphosate (0.0, 115.2 and 460.8 g acid equivalent ha-1 ), in a factorial 3 x 3 design. At 15 days after application, a reduction in stomatal conductance was observed, and smaller transpiration rate and water use efficiency were found in the fourth leaf at 15 days after application. There was a decrease in the transpiration rate at 45 DAA, with the Acaiá cultivar showing reductions with 115.2 g ha-1 . There was transitory reduction in water use efficiency with glyphosate application, but can affect the growth and production. The Acaiá cultivar showed the highest tolerance to glyphosate because the water use efficiency after herbicide application.