Efeito de herbicidas com diferentes mecanismos de ação no controle e na fisiologia e bioquímica de caruru rasteiro sob condições de estresse abiótico

• Ano de defesa: 2014
• Autor(a) principal: Fontes, Larissa de Oliveira
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Amaranthus deflexus L.; Matologia; Controle químico; Estresse hídrico; Alterações bioquímicas
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/39583

This research was conducted aiming to obtain basic data that could help in the understanding of the effect of herbicides of different mechanisms of action in the phytotoxicity and in physiologic and biochemical characteristics of Amaranthus deflexus L. under different conditions of abiotic stress. In the first two chapters, seeds were placed in Petri dishes containing two sheets of filter paper moistened with distillated water (control) and polyethylene glycol 6000 (PEG 6000) in order to achieve the osmotic potential of -0.3, -0.6, -0.9, -1.2, and -1.5 MPa in experiment one and -0.1, -0.2, -0.3, -0.4, and -0.5 MPa in experiment two. In the first experiment of the second chapter it was used the same plot as in the first experiment of the previous chapter. In this case, polyethylene glycol 6000 (PEG 6000) was replaced by NaCl. At the end of the experiments, the seeds that did not germinate in each treatment were washed and placed on filter paper moistened with water in order to observe the continuity of the germination process. In both experiments it was used a completely randomized 2x 6 factorial design in which the first factor was photoperiod (12 hours of light and 24 hours of darkness) and the second factor was level of hydric or salt conditions, in a total of twelve treatments with for replications of 50 seeds each. In the second experiment of the second chapter, fifty seeds were kept under continuous temperatures of 20; 25; 30; 35 and 40 °C, and alternating temperatures of 20-30; 25-35 and 30-40 °C. Germination and vigor of A. deflexus seeds were evaluated through first germination count, germination test, germination speed index, and average germination time. In the third chapter, it was evaluated the influence of herbicides via different mechanisms of action and different hydric conditions on the initial establishment of A. deflexus. It was used a completely randomized design with double factorial and subplots split over the time. The analysis of variance was done using the mixed model methodology. The variables were the total dry mass, plant height, stem diameter, relative water content, and the relative percentage of chlorophyll. The weed was subjected to: (i) three products (water, glyphosate, diuron, nicosulfuron and 2.4 D), (ii) hydric conditions (100, 60 and 30% of field capacity) and (iii) time (0, 2, 4, 6 and 8 days) after the application of the products in a total of 75 combinations. In order to determine phytotoxicity, evaluations were conducted from two to eight days after the application of herbicides. In the fourth chapter, it was evaluated the effect of herbicides sprayed after emergence of A. deflexus plants on activity of antioxidant enzymes subjected to different hydric conditions. It was used a completely randomized design with double factorial and subplots split over the time. The analysis of variance was done using the mixed model methodology. It was analyzed the enzymatic activity of catalase, superoxide dismutase, ascorbate peroxidase and guaicol peroxidase. The weed was subjected to: (i) three products (water, glyphosate, diuron, nicosulfuron and 2.4 D), (ii) hydric conditions (100, 60 and 30% of field capacity) and (iii) time (24, 48, and 72 hours) after the application of the products in a total of 45 combinations. Hydric and salt stress affected negatively the development of A. deflexus seeds by reducing their germination and vigor from -0,1 MPa on. The germination of A. deflexus seeds was reduced by the absence of light regardless of the level hydric or salt stress applied. There was an increase in the germination of A. deflexus seeds after the rehydration of the ones subjected to the higher levels of hydric and salt stress. The final percentage of germination and the speed germination index of A. deflexus seeds were superior at the continuous temperature of 25 °C and at the alternating temperatures of 25-35 °C. It was found a reduction in the quantitative characteristics of growth in A. deflexus plants as a function of the application of herbicides in association with hydric stress. In relation to the random variation caused by the accumulation of time in the subplots, it was found that the tendency of reduction in the height, stem diameter, total dry mass, total percentage of chlorophylle and relative water content of plants. There was an increase in the phytotoxicity to weeds up to the eighth day after the application of herbicides following prolongation in the interval of evaluation. There was a reduction in the activity of the antioxidant enzymatic system in A. deflexus seeds as a function of the application of herbicides in association with different hydric conditions.