Fitotoxidez de mesotriona em milho inoculado com Azospirillum brasilense associado a adubação nitrogenada

Abstract

RESUMOEste estudo objetivou avaliar a fitotoxidez do herbicida mesotriona no desenvolvimento inicial do milho inoculado com Azospirillum brasilense, associado à adubação nitrogenada. O delineamento utilizado foi o de blocos casualizados, em esquema fatorial 2x3, representado por milho com e sem aplicação do mesotriona (192 g ha) e os tratamentos: 1-inoculação das sementes com A. brasilense; 2-aplicação em cobertura de 140 kg ha -1 de N; e 3-A. brasilense + 140 kg ha -1 de N em cobertura aplicado aos 26 dias após a semeadura (DAS). A aplicação do mesotriona foi realizada aos 21 DAS, com avaliações realizadas por 28 dias após a aplicação (DAA). Aos 7 DAA constatou-se redução da taxa de assimilação líquida de CO 2 em 35% nas plantas que receberam aplicação de mesotriona, bem como aumento da atividade da peroxidase e maior degradação de carotenoides. Aos 14 DAA de mesotriona resultou em redução na taxa de assimilação líquida de CO 2 e na transpiração, enquanto aos 28 DAA foi verificado menor altura de plantas, área foliar e massa seca de parte aérea nas plantas com herbicida. A inoculação com A. brasilense + N elevou a atividade das peroxidases aos 7 DAA e auxiliou a manutenção da taxa transpiratória aos 14 DAA. Conclui-se que a inoculação com A. brasilense + N pode minimizar os efeitos danosos causados pelo mesotriona no desenvolvimento inicial do milho.Palavras-chave: bactérias promotoras de crescimento vegetal; herbicida; inibidor dos carotenoides; trocas gasosas Phytotoxicity of mesotriona in corn with Azospirillum brasilense associated nitrogen fertilization ABSTRACTThis study aimed to evaluate the phytotoxicity of the mesotrione herbicide in the initial development of maize inoculated with Azospirillum brasilense and associated with nitrogen fertilization. The treatments were: randomized blocks in a 2x3 factorial scheme, represented by maize with and without mesotrione application (192 g ha -1 ) and treatments: 1-inoculation of the seeds with A. brasilense; 2-Application in coverage of 140 kg ha -1 of N; And 3-A. brasilense + 140 kg ha-1 of N in cover applied at 26 days after sowing (DAS). The application of mesotrione was performed at 21 DAS, with evaluations performed up to 28 days after application (DAA). At 7 DAA a reduction of the net assimilation rate of CO 2 in 35% in the plants with mesotrione was observed, as well as increase of the peroxidases activity and greater degradation of carotenoids in the mesotrione plants. At 14 DAA the mesotrione reduced the rate of CO 2 net assimilation and transpiration, while at 28 DAA, lower plant height, leaf area and shoot dry mass were verified in herbicide plants. The inoculation with A. brasilense + N increased peroxidase activity at 7 DAA and helped maintain the transpiratory rate at 14 DAA. It is concluded that inoculation with A. brasilense + N can minimize the harmful effects caused by mesotrione in the initial development of corn.

Biometric and Bromatological Characteristics of Brachiaria Inoculated With Azospirillum brasilense Associated With Nitrogen Fertilization

“…When considering the supply caused by the plant growth promotion bacteria A. brasilense, it is observed that the results of the present study are inconclusive in relation to the capacity to raise the dry mass of plants. These results may have occurred by the cultivation condition, which was in pots, where the increases in the root system are limited by its exploration area, as that no hydric limitation occurred, condition where the use of A. brasilense brings increases to tropical pastures (Bulegon, Inagaki, Moratelli, Costa, & Guimarães, 2017). It is worth mentioning that the absence of conclusive results in the present study, provided by the inoculation with A. brasilense, may be associated with the genetic characteristics of the used material, where the study was conducted beyond the intervals between inoculation and evaluation (Alcântara, 2018).…”

Intoxication of Mesotrione in Corn Inoculated with Azospirillum brasilense and with Application of Plant Growth Regulators

“…However, although mesotrione is a selective herbicide for use in maize, it can cause up to 35% intoxication (Bulegon et al, 2017), which is characterized by white spots in the new leaves of maize plants. Such spots become chlorotic and there is subsequent necrosis of the leaf tissue in the most extreme conditions (Barchanska et al, 2014), thereby interfering with crop plant metabolism (O'Sullivan et al, 2002;Ogliari et al, 2009).…”